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/install-apply.js

@@ -27,11 +27,12 @@ Usage: install.sh [--target <${LEGACY_INSTALL_TARGETS.join('|')}>] [--dry-run] [
        install.sh [--target <${SUPPORTED_INSTALL_TARGETS.join('|')}>] [--dry-run] [--json] --profile <name> [--with <component>]... [--without <component>]...
        install.sh [--target <${SUPPORTED_INSTALL_TARGETS.join('|')}>] [--dry-run] [--json] --modules <id,id,...> [--with <component>]... [--without <component>]...
        install.sh [--target <${SUPPORTED_INSTALL_TARGETS.join('|')}>] [--dry-run] [--json] --skills <skill-id[,skill-id...]>
-       install.sh [--target claude] [--dry-run] [--json] --locale <locale-code>
+       install.sh [--target claude|claude-project] [--dry-run] [--json] --locale <locale-code>
        install.sh [--dry-run] [--json] --config <path>
 
 Targets:
   claude       (default) - Install ECC into ~/.claude/ with managed rules/skills under rules/ecc and skills/ecc
+  claude-project - Install ECC into ./.claude/ (per-project) with managed rules/skills under rules/ecc and skills/ecc
   cursor       - Install rules, hooks, and bundled Cursor configs to ./.cursor/
   antigravity  - Install rules, workflows, skills, and agents to ./.agent/
   codex        - Install shared agents/config into ~/.codex/
@@ -49,8 +50,8 @@ Options:
   --skills <ids>      Install one or more skill directories by ID, e.g. continuous-learning-v2
   --without <component>
                       Exclude a user-facing install component
-  --locale <code>     Install translated docs to ~/.claude/docs/<locale>/
-                      (claude target only; can be combined with --profile or --with)
+  --locale <code>     Install translated docs to ~/.claude/docs/<locale>/ (or ./.claude/docs/<locale>/ for claude-project)
+                      (claude or claude-project target only; can be combined with --profile or --with)
   --config <path>     Load install intent from ecc-install.json
   --dry-run    Show the install plan without copying files
   --json       Emit machine-readable plan/result JSON