Update the documentation to match what the code does

The README told people there was no System Extension to install; now it says
the subsystem was removed and why, and that userspace IOKit is the whole
mechanism. Three documents went with it:

- Documentation/development/system-extension-development.md described a
  build flow — `swift build --product SystemExtension`, `sudo usbipd daemon
  --install-extension` — for a product and a flag that no longer exist. The
  product name was wrong even before this change.
- Documentation/troubleshooting/system-extension-troubleshooting.md
  troubleshot a subsystem that is gone.
- Documentation/homebrew-troubleshooting.md was written throughout against a
  formula named usbipd-mac, which has never existed — the formula is usbip.
  Every command in it failed: brew install usbipd-mac, brew services start
  usbipd-mac, the log path, the launchd plist names, and an untap of a tap
  that is not the tap. It also omitted the brew trust step the README
  documents as mandatory. Deleting it is better than rewriting 632 lines of
  guesses; the true parts are already in the README.

`sudo usbipd daemon --install-extension` is removed from architecture.md,
build-troubleshooting.md and Emergency-Release-Procedures.md. That flag does
not exist and never did.

CLAUDE.md had three claims that were false. It described the subsystem as
quarantined rather than removed; it said both test targets compile
Tests/SharedUtilities/, which SwiftPM has never done because it ignores
`sources:` paths outside the target directory — AssertionHelpers.swift
references config.autoBindDevices, deleted long ago, and so cannot compile;
and it reported 397 tests when there are 429.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017rmyikdjWveP99ZUCDLY89

Author: beriberikix

CHANGELOG.md

@@ -7,6 +7,56 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Removed — the System Extension subsystem
+
+Some 24,000 lines that no shipping path could reach, and a release artifact no
+installed component could locate.
+
+Activation was never attempted: both `OSSystemExtensionManager.submitRequest` call
+sites were unreachable, gated on a configuration value nothing ever set. The whole of
+`Sources/SystemExtension/` was unreachable even from its own executable, its types
+shadowed by same-named stubs. `usbipd status` had 600 lines of reporting behind a guard
+that always took the early return.
+
+None of it could have worked. `OSSystemExtensionRequest` resolves extensions inside the
+calling process's own bundle and requires that bundle to live in `/Applications`; a
+Homebrew-installed binary is neither. The claiming strategy underneath — setting
+`IOMatchCategory` and `IOProbeScore` from userspace — was measured not to unbind
+anything, and is not how a DriverKit extension matches in any case.
+
+Nothing that worked has changed. Devices macOS has not bound a driver to are served
+exactly as before; devices whose interfaces it holds are refused by `bind`, which names
+the owner. Those decisions were always made by `DeviceOwnershipInspector` and by IOKit
+refusing `USBInterfaceOpen`, not by the extension.
+
+**User-visible changes:**
+
+- `USBIPDSystemExtension.systemextension.tar.gz` is no longer published. It was signed,
+  notarized and stapled every release, and was not a System Extension bundle by
+  structure — no `NSExtension` dict, no `IOKitPersonalities`, and an empty
+  `embedded.provisionprofile`.
+- `systemextension_url` and `systemextension_sha256` are gone from the Homebrew
+  metadata. Nothing consumed them.
+- `usbipd status` reports how devices are accessed and which are shared, and no longer
+  claims to report on an extension. `--health` is still accepted and says plainly that
+  there is nothing further to check.
+- `bind` and `unbind` no longer print "Checking System Extension status..." or branch
+  their success message on whether a manager existed.
+- `~/Library/Application Support/usbipd-mac/cli-claimed-devices.json` is no longer read
+  or written. It recorded claims that were never taken; any existing file is inert and
+  can be deleted.
+- `usbipd.entitlements` is gone. The binary carried
+  `com.apple.developer.system-extension.install`, a restricted entitlement AMFI kills
+  without an authorising profile, so release signing had to withhold it — which it
+  always did. With nothing to install, signing has one path.
+
+`Sources/SystemExtension/Info.plist`, its entitlements and the README explaining the
+failure are preserved under `Documentation/development/system-extension-archive/`. They
+record the identifier and entitlement decisions a future DriverKit extension needs.
+
+Also corrected: `CLAUDE.md` claimed `Tests/SharedUtilities/` was compiled by both test
+targets. SwiftPM ignores `sources:` paths outside the target directory, so it never was.
+
 ## [v0.6.0] - 2026-08-09
 
 This release makes usbipd usable on a machine with a USB hub, which in practice means

CLAUDE.md

@@ -91,10 +91,14 @@ Isochronous is not merely untested but structurally incomplete: alternate settin
 never selected and pipes are discovered once at open, so a UVC device's isochronous
 endpoints would never appear. See `Documentation/development/probe-rs-validation.md`.
 
-The **SystemExtension** target is quarantined — roughly 20,000 lines that no shipping
-path uses. `OSSystemExtensionRequest` resolves extensions inside the calling app's
-bundle and requires that bundle to live in `/Applications`, so a Homebrew install
-never consults it. See `Sources/USBIPDCore/SystemExtension/README.md`.
+The **SystemExtension subsystem was removed in 0.7.0** — some 24,000 lines that no
+shipping path could reach. `OSSystemExtensionRequest` resolves extensions inside the
+calling process's own bundle and requires that bundle to live in `/Applications`, so a
+Homebrew install could never activate one; the claiming strategy underneath was measured
+not to unbind anything either. `DeviceClaimManager` survives as the seam a real
+implementation would slot into, satisfied by `UserspaceDeviceClaimManager`, which tracks
+intent and says so. See
+`Documentation/development/system-extension-archive/why-it-was-removed.md`.
 
 ## Architecture
 
@@ -107,7 +111,6 @@ The project is structured as a multi-target Swift package:
   - `Protocol/`: USB/IP message encoding/decoding and request processing
 - **USBIPDCLI**: Command-line interface executable (`usbipd` binary)
 - **Common**: Shared utilities (logging, error handling)
-- **SystemExtension**: quarantined; no shipping path activates it (see above)
 - **QEMUTestServer**: QEMU validation test server
 
 ### Test Structure
@@ -117,7 +120,10 @@ The project is structured as a multi-target Swift package:
 - **Tests/USBIPDCoreTests/** — core protocol, device, and network tests
 - **Tests/USBIPDCLITests/** — CLI behaviour
 
-Both also compile **Tests/SharedUtilities/** via their `sources:` list.
+Both list **Tests/SharedUtilities/** in their `sources:`, but SwiftPM silently ignores
+source paths outside the target directory, so it is **not compiled**. Proof beyond the
+build plan: `AssertionHelpers.swift` references `config.autoBindDevices`, which no
+longer exists. Do not add tests there expecting them to run.
 
 Three further targets are declared but commented out as "temporarily disabled":
 `IntegrationTests`, `SystemExtensionTests`, `QEMUIntegrationTests`. Alongside them
@@ -251,7 +257,7 @@ The project uses a comprehensive SwiftLint configuration (`.swiftlint.yml`) with
 
 ## Testing Strategy
 
-`swift test --parallel` is the whole suite — 397 tests across `USBIPDCoreTests` and
+`swift test --parallel` is the whole suite — 429 tests across `USBIPDCoreTests` and
 `USBIPDCLITests`. There is no development/CI/production tier system; the scripts that
 claimed to provide one filtered on target names that were never declared, matched
 nothing, and exited 0. See `Documentation/development/testing-strategy.md`.

Documentation/Emergency-Release-Procedures.md

@@ -202,7 +202,6 @@ For System Extension issues:
 sudo systemextensionsctl uninstall [team-id] [bundle-id]
 
 # 2. Install previous version
-sudo usbipd daemon --install-extension --version v1.2.3
 
 # 3. Verify rollback
 usbipd status

Documentation/README.md

@@ -20,7 +20,6 @@ The `development/` folder contains detailed documentation for contributors:
 - **[Unwired code sweep](development/unwired-code-sweep.md)** - finding mechanisms nothing calls, and what that found
 - **[Architecture](development/architecture.md)** - System design and component overview
 - **[CI/CD](development/ci-cd.md)** - Continuous integration and deployment workflows
-- **[System Extension Development](development/system-extension-development.md)** - macOS System Extension integration
 - **[Testing Strategy](development/testing-strategy.md)** - Testing approaches and environments
 
 ## API Reference
@@ -35,7 +34,6 @@ The `troubleshooting/` folder contains problem resolution guides:
 
 - **[Build Troubleshooting](troubleshooting/build-troubleshooting.md)** - Common build and setup issues
 - **[QEMU Troubleshooting](troubleshooting/qemu-troubleshooting.md)** - QEMU testing issues
-- **[System Extension Troubleshooting](troubleshooting/system-extension-troubleshooting.md)** - System Extension development issues
 
 ## Navigation
 

Documentation/deployment-checklist.md

@@ -414,7 +414,6 @@ which jq curl shasum
 
 After deployment, ensure these documents are updated:
 - [ ] **README.md**: Installation instructions point to tap repository
-- [ ] **Documentation/homebrew-troubleshooting.md**: Includes tap-specific troubleshooting
 - [ ] **CLAUDE.md**: Reflects new development workflows
 - [ ] **Release notes**: Document the architecture change for users
 

Documentation/development/architecture.md

@@ -85,7 +85,6 @@ System Extensions are installed automatically when the USB/IP daemon starts:
 
 ```bash
 # Install and activate System Extension
-sudo usbipd daemon --install-extension
 
 # Check System Extension status
 usbipd status
@@ -138,7 +137,6 @@ sudo systemextensionsctl developer on
 
 # Build and install for development
 swift build
-sudo usbipd daemon --install-extension
 
 # Verify installation
 usbipd status