Add GitHub Copilot hook support (CLI + cloud agent) (#279)

* Add GitHub Copilot hook support (CLI + cloud agent)

Wire the Impeccable design detector into GitHub Copilot's hook system so
direct file edits get the same post-edit design feedback the Claude Code,
Codex, and Cursor harnesses already receive.

GitHub Copilot's contract differs from the existing harnesses (verified
against Copilot CLI 1.0.63):
- Repo-level manifest at `.github/hooks/impeccable.json` (read by both the
  CLI, once committed to the default branch, and the cloud/app agent).
- Flat `postToolUse` entries with `bash`/`timeoutSec` and a full-match
  `matcher` regex; the file-editing tools are `edit` and `create`.
- The stdin event uses camelCase `toolName`/`toolArgs`, where `toolArgs` is
  a JSON *string* carrying the touched file under `path`.
- Context is injected via a top-level `additionalContext` string.

Changes:
- hooks.js: buildGitHubHooksManifest() + route `github` in hooksJsonFor().
- providers.js: emitHooks/hooksManifestRel for the github provider.
- hook-lib.mjs: detect the github harness, normalize the camelCase event
  (parse the JSON-string toolArgs -> tool_input.file_path), and emit the
  `additionalContext` payload shape.
- hook-admin.mjs / skills.mjs: install + idempotent-repair the
  `.github/hooks/impeccable.json` manifest (bash-aware marker stripping).
- hooks.md: document GitHub Copilot as a supported harness.
- Tests for the builder, routing, event normalization, and end-to-end run.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Cover Copilot apply_patch edits in the hook (live-verified)

The first cut matched only `edit|create`, the tool names `copilot -p` uses.
A live trace against Copilot CLI 1.0.63 in an interactive session showed it
edits files via `apply_patch`, whose toolArgs is a raw OpenAI-format patch
string (`*** Begin Patch` / `*** Add File:`), not JSON. With the narrow
matcher the hook command never ran.

- hooks.js / hook-admin.mjs: matcher -> `edit|create|apply_patch`.
- hook-lib.mjs: normalizeGitHubEvent now routes apply_patch's raw patch
  string into tool_input.command (reusing the existing parseApplyPatchPaths /
  resolveTargetFiles plumbing) and only JSON-parses toolArgs for the
  edit/create/view tools. tool_name is normalized to apply_patch so the patch
  path is extracted even if a future build relabels the tool.
- Tests: apply_patch matcher assertions, event normalization, and an
  end-to-end runHook covering the interactive/cloud path.

Verified live: a trusted interactive `apply_patch` edit fires the hook and
returns the expected `additionalContext` design reminder.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Address review feedback + add changelog entry

- hook-lib.mjs (Bugbot, low): looksLikeApplyPatch no longer misroutes an
  edit/create event whose edited *content* contains apply_patch markers. A
  real apply_patch payload is a raw string that does not parse as JSON; an
  edit payload is a JSON object, so only non-JSON-object strings are treated
  as apply_patch. Edit events keep extracting `path`. Adds a regression test.
- skills.mjs (Bugbot, medium): document why `.github` is intentionally
  excluded from hookScriptPathForProvider. Its hook manifest is committed and
  shared (read by the Copilot cloud agent and teammates), so the command must
  stay portable via `$(git rev-parse ...)`; rewriting it to a machine-local
  absolute path would break those. GitHub skills are project-scoped, so the
  project-relative path resolves.
- changelog: add an Upcoming (v3.x placeholder) entry for the Copilot hook.
  Version is not bumped yet (batching with other changes).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/lib/transformers/hooks.js

@@ -24,6 +24,7 @@ const CLAUDE_PROJECT_HOOK = '${CLAUDE_PROJECT_DIR}/.claude/skills/impeccable/scr
 const CLAUDE_PLUGIN_HOOK = '${CLAUDE_PLUGIN_ROOT}/skills/impeccable/scripts/hook.mjs';
 const CODEX_PROJECT_HOOK = '$(git rev-parse --show-toplevel)/.agents/skills/impeccable/scripts/hook.mjs';
 const CURSOR_BEFORE_EDIT_SCRIPT = '.cursor/skills/impeccable/scripts/hook-before-edit.mjs';
+const GITHUB_PROJECT_HOOK = '$(git rev-parse --show-toplevel)/.github/skills/impeccable/scripts/hook.mjs';
 
 export function buildClaudeSettingsManifest() {
   return {
@@ -106,6 +107,33 @@ export function buildCursorHooksManifest() {
   };
 }
 
+// GitHub Copilot reads project hooks from `.github/hooks/*.json`. Its schema
+// differs from Claude/Codex/Cursor: the event key is lowercase `postToolUse`,
+// each entry is flat (no nested `hooks` array), the command lives under `bash`
+// (with an optional `powershell` sibling), the timeout key is `timeoutSec`, and
+// `matcher` is a full-match regex (`^(?:PATTERN)$`) tested against the tool name.
+// Copilot's file-editing tool names vary by surface (verified against CLI
+// 1.0.63): `copilot -p` runs use `edit` ({path, old_str, new_str}) and `create`
+// ({path, file_text}); interactive sessions and the cloud agent use
+// `apply_patch` (a raw OpenAI-format patch string). The matcher covers all
+// three. The same manifest is honored by both the CLI and the cloud/app agent.
+// https://docs.github.com/en/copilot/reference/hooks-reference
+export function buildGitHubHooksManifest() {
+  return {
+    version: 1,
+    hooks: {
+      postToolUse: [
+        {
+          type: 'command',
+          matcher: 'edit|create|apply_patch',
+          bash: `node "${GITHUB_PROJECT_HOOK}"`,
+          timeoutSec: TIMEOUT_SECONDS,
+        },
+      ],
+    },
+  };
+}
+
 export function hooksJsonFor(provider) {
   switch (provider) {
     case 'claude':
@@ -114,6 +142,8 @@ export function hooksJsonFor(provider) {
       return buildCodexHooksManifest();
     case 'cursor':
       return buildCursorHooksManifest();
+    case 'github':
+      return buildGitHubHooksManifest();
     default:
       return null;
   }

scripts/lib/transformers/providers.js

@@ -68,6 +68,9 @@ export const PROVIDERS = {
     displayName: 'GitHub Copilot',
     placeholderProvider: 'agents',
     frontmatterFields: ['user-invocable', 'argument-hint', 'license', 'compatibility', 'metadata'],
+    emitHooks: 'github',
+    // GitHub Copilot discovers repo-level hooks under `.github/hooks/*.json`.
+    hooksManifestRel: 'hooks/impeccable.json',
   },
   kiro: {
     provider: 'kiro',