feat: add check command for CI validation predicates (#225)

* feat: add batch querying for multi-agent dispatch

Add `codegraph batch <command> [targets...]` CLI command, `batchData()`
programmatic API, and `batch_query` MCP tool. Runs the same query
against multiple targets in one call, returning all results in a single
JSON payload with per-target error isolation.

Supports 10 commands: fn-impact, context, explain, where, query, fn,
impact, deps, flow, complexity. Accepts targets via positional args,
--from-file (JSON array or newline-delimited), or --stdin.

Impact: 3 functions changed, 3 affected

* fix: correct spread order in batch.js comments to match implementation

Impact: 1 functions changed, 1 affected

* feat: add `check` command for CI validation predicates

Composable validation predicates that run against git changes (staged or
vs a ref) and return exit code 0/1 for CI gates and pre-commit hooks.

Four predicates: --cycles (no dependency cycles involving changed files),
--blast-radius <n> (no function exceeds N transitive callers),
--signatures (no function declaration lines modified), --boundaries
(no cross-owner CODEOWNERS violations). All boolean predicates enabled
by default; configurable via .codegraphrc.json `check` section.

Impact: 7 functions changed, 3 affected

* fix: sort check export alphabetically in index.js

Author: carlos-alm