feat(install-targets): add claude-project (per-project Claude Code) adapter

Completes the install-target matrix for Claude Code. Until now, ECC's
Claude support was home-scope only (~/.claude/) via the `claude` target.
This adds a project-scope counterpart (./.claude/) via a new
`claude-project` target so teams can install ECC per-repo without
contaminating ~/.claude/ — matching the existing project-scope adapters
for Cursor, Antigravity, Gemini, CodeBuddy, Joycode, and Zed.

Symmetric with `claude`:
- Same namespace under rules/ecc and skills/ecc
- Same docs/<locale> handling for --locale
- Same hooks placeholder substitution for hooks.json
- Reuses claude-home's destination-mapping logic 1:1

Use cases:
- Monorepos with multiple Flow-managed projects
- Teams that want ECC scoped per-project without touching ~/.claude/
- Per-project skill/rule isolation when global install isn't desirable

No breaking change: existing --target claude continues to route to
claude-home (user-scope) unchanged. New target is opt-in.

Tests
-----
- 4 new tests in tests/lib/install-targets.test.js
  (root resolution, lookup-by-id, plan parity with claude, foreign-path filtering)
- All install-target regression guards (schema enum / SUPPORTED_INSTALL_TARGETS)
  still pass
- End-to-end smoke: `--target claude-project --profile minimal --dry-run`
  emits 359 ops with destinations rooted at <projectRoot>/.claude/ (parity
  with --target claude which emits 359 ops rooted at ~/.claude/)

scripts/lib/install-manifests.js

@@ -4,7 +4,7 @@ const path = require('path');
 const { getInstallTargetAdapter, planInstallTargetScaffold } = require('./install-targets/registry');
 
 const DEFAULT_REPO_ROOT = path.join(__dirname, '../..');
-const SUPPORTED_INSTALL_TARGETS = ['claude', 'cursor', 'antigravity', 'codex', 'gemini', 'opencode', 'codebuddy', 'joycode', 'qwen', 'zed'];
+const SUPPORTED_INSTALL_TARGETS = ['claude', 'claude-project', 'cursor', 'antigravity', 'codex', 'gemini', 'opencode', 'codebuddy', 'joycode', 'qwen', 'zed'];
 const COMPONENT_FAMILY_PREFIXES = {
   baseline: 'baseline:',
   language: 'lang:',
@@ -43,6 +43,14 @@ const LEGACY_COMPAT_BASE_MODULE_IDS_BY_TARGET = Object.freeze({
     'platform-configs',
     'workflow-quality',
   ],
+  'claude-project': [
+    'rules-core',
+    'agents-core',
+    'commands-core',
+    'hooks-runtime',
+    'platform-configs',
+    'workflow-quality',
+  ],
   cursor: [
     'rules-core',
     'agents-core',