feat(targets): add multi-target CLI adapter system (Droid support)

Implement target adapter pattern enabling CCS CLI to support multiple backend targets
(Claude, Droid) via pluggable adapters. Core additions:

- TargetAdapter interface for pluggable target implementations
- ClaudeAdapter and DroidAdapter concrete implementations
- Target registry (singleton Map-based storage)
- Target resolver with precedence: --target flag > per-profile config > busybox detection
- Droid config manager with atomic writes and file locking to ~/.factory/settings.json
- Droid binary detector to validate runtime environment
- Adapter dispatch integrated into ccs.ts main execution flow
- ccsd busybox alias for seamless Droid invocation
- --target flag documentation in help
- Session tracking enriched with target metadata
- Dashboard target badge for visual identification

Testing:
- 43 unit tests covering resolver, registry, config manager, and adapters
- Full coverage of target detection logic and edge cases

Documentation:
- Refactored system-architecture.md into modular docs/system-architecture/ subdirectory
- Updated code-standards.md with target adapter guidelines
- Updated codebase-summary.md with architecture overview
- Updated maintainability baseline (33.8% → 35.2%)

This establishes extensible foundation for multi-target support without breaking
existing Claude workflows. Droid adapter is production-ready but defaults to Claude
for backward compatibility.

package.json

@@ -26,7 +26,8 @@
   "main": "dist/ccs.js",
   "types": "dist/ccs.d.ts",
   "bin": {
-    "ccs": "dist/ccs.js"
+    "ccs": "dist/ccs.js",
+    "ccsd": "dist/ccs.js"
   },
   "files": [
     "dist/",
@@ -102,6 +103,7 @@
     "listr2": "^3.14.0",
     "open": "^8.4.2",
     "ora": "^5.4.1",
+    "proper-lockfile": "^4.1.2",
     "ws": "^8.16.0"
   },
   "devDependencies": {
@@ -121,6 +123,7 @@
     "@types/express-session": "^1.18.2",
     "@types/js-yaml": "^4.0.9",
     "@types/node": "^20.19.25",
+    "@types/proper-lockfile": "^4.1.4",
     "@types/ws": "^8.5.10",
     "@typescript-eslint/eslint-plugin": "^8.48.0",
     "@typescript-eslint/parser": "^8.48.0",