v3.14.0

Added

• Feat(mcp): add search_existing_implementations as a native MCP tool + CLI

What changed:

• NEW MCP tool: search_existing_implementations (index.ts, ~320 lines).
  Walks the target folder(s), filters by language extension (auto-
  detected from source_files if not supplied), excludes source_files
  from the scan list to avoid self-match, builds the specialized
  yes/no prompt internally, and dispatches each file to the LLM
  pipeline (ensemble mode, auto-batching, per-file retry, circuit
  breaker). Output per file is terse: one line of NO, NO
  (self-reference), or YES symbol= lines= (max 5 per file).

• NEW CLI subcommand: llm-externalizer search-existing (cli.ts).
  Spawns the MCP server via StdioClientTransport, calls the tool,
  prints the text result, exits. Supports all tool options plus
  --base <ref> (auto-generates the PR diff via
  git diff <ref>...HEAD -- <src-files>) and --diff <path> as an
  escape hatch. Auto-detects the base branch from origin/HEAD → main
  → master when neither flag is given and source files are provided.

• Slash command /search-existing-implementations: rewritten as a
  thin 4824-char wrapper (was 13121 chars). Now just calls the MCP
  tool; all heavy logic lives in the server handler.

Inputs (all but one are optional):

• feature_description MANDATORY — drives the LLM prompt
• folder_path MANDATORY — single or list of codebase paths
• source_files OPTIONAL — reference files; excluded from scan
• diff_path OPTIONAL — narrows focus to new lines
• extensions, exclude_dirs, max_files, scan_secrets, redact_secrets,
  answer_mode, redact_regex, use_gitignore, max_payload_kb — same
  semantics as scan_folder

Why native MCP tool instead of slash-command-only:

• Usable from any MCP client, not just Claude Code
• Accessible from shell / CI via the CLI subcommand
• Subagents can call it via mcp__ tool calls
• The specialized yes/no prompt template lives server-side, so it
  doesn't need to be re-implemented in every caller
• Consistent auto-batching, retry, and ensemble semantics with the
  other llm-externalizer tools

Tests:

• index.test.ts: expected tools list now includes
  search_existing_implementations alphabetically between
  scan_folder and set_settings. All 18 unit tests pass.
• CLI smoke-tested: missing description aborts with a clean error,
  missing --in aborts with a clean error, --help shows the new
  command with all flags documented.

Verified: claude plugin validate . ✓, CPV remote validation ✓
(CRITICAL=0 MAJOR=0 MINOR=0), npm run typecheck ✓, npm run lint ✓,
npm run build ✓ (fully bundled dist/), npm test 18/18 ✓.