add testmode skill for ClideTestApp harness

Teaches Claude when and how to use make run-testmode, which
category to run for a given change, how to interpret output,
and the pattern for adding new test cases.

Co-Authored-By: Claude <noreply@anthropic.com>

.claude/skills/testmode/SKILL.md

@@ -0,0 +1,86 @@
+---
+name: testmode
+description: >
+  Run and interpret the ClideTestApp platform integration harness.
+  Use after modifying toolchain resolution, IPC dispatch, extension
+  lifecycle, theme loading, or native platform code. Also use when
+  the user says "run testmode", "test the app", "smoke test", or
+  "verify the build". Triggers on changes to: lib/kernel/src/toolchain.dart,
+  lib/src/daemon/dispatcher.dart, lib/src/ipc/, lib/extension/,
+  lib/kernel/src/theme/, lib/builtin/*/src/extension.dart,
+  linux/CMakeLists.txt, macos/, Makefile (run targets), lib/main.dart.
+---
+
+# Testmode harness
+
+`ClideTestApp` is a lightweight Flutter app that boots the real platform
+layer, runs structured tests, prints results, and exits. It catches
+regressions that unit tests cannot see: missing binaries, broken
+subprocess wiring, IPC dispatch failures, extension activation order,
+and theme parse errors.
+
+## Running
+
+```bash
+make run-testmode                          # all categories
+make run-testmode TESTMODE_CATEGORY=toolchain
+make run-testmode TESTMODE_CATEGORY=ipc
+make run-testmode TESTMODE_CATEGORY=extensions
+```
+
+Results go to stdout **and** `/tmp/clide-testmode.log`. The last line
+of testmode output is machine-readable:
+
+```
+[testmode:json] {"passed":33,"failed":0,"total":33,"failures":[]}
+```
+
+Exit code is non-zero when any test fails. The Makefile verifies
+`"failed":0` in the log via `grep -q`.
+
+## When to run which category
+
+| Changed area | Category | Why |
+|---|---|---|
+| Toolchain, PATH, dugite, ptyc, shell | `toolchain` | Binary resolution + exec |
+| IPC envelope, dispatcher, schema | `ipc` | Round-trip + error contract |
+| Extension manifest, activate, contributions | `extensions` | Register + activate lifecycle |
+| Theme YAML, loader, palette | `extensions` | Theme parse is in this category |
+| Platform config (CMakeLists, pbxproj, Makefile) | `all` | Full rebuild validates everything |
+| Any doubt | `all` | ~30s, cheap insurance |
+
+## Interpreting output
+
+- `[testmode] exec | ... | OK` — subprocess ran, exit 0 or 1.
+- `[testmode] PASS | ...` — assertion passed (IPC / extension tests).
+- `[testmode] FAIL | ...` — assertion failed. The output column says why.
+- `[testmode] exec | ... | EXCEPTION` — binary not found or not executable.
+- `[testmode] exec | ... | TIMEOUT` — subprocess hung (5s limit).
+
+If the app never prints `[testmode]` lines, the testmode gate in
+`main.dart` didn't fire — check that `CLIDE_TESTMODE` is set to a
+non-empty string (not a bare bool).
+
+## Adding tests
+
+All test logic lives in `lib/test_app.dart`. Pattern:
+
+```dart
+// In the appropriate _run*Tests method:
+await _testExec('label', binary, ['args'], workDir);
+// or
+_addResult('label', boolCondition, 'detail string');
+```
+
+New categories: add a `runFoo` bool from the `category` string,
+gate a new `_runFooTests` method, and add the category name to
+the Makefile help comment and this skill's table above.
+
+Extension tests must include transitive dependencies — e.g.
+`GitExtension` requires `DiffExtension` to activate first.
+
+## Source files
+
+- `lib/test_app.dart` — all test logic and UI
+- `lib/main.dart:54` — testmode gate (`String.fromEnvironment`)
+- `Makefile:42–56` — `run-testmode` target with category variable

.pql/pql-plan.json

@@ -1,5 +1,5 @@
 {
-  "exported_at": "2026-04-26T11:45:43Z",
+  "exported_at": "2026-04-26T11:47:30Z",
   "decisions": [
     {
       "id": "D-1",