v0.3.0 — self-improving recall

Recall now gets better with use: engram reinforce "<query>" <source> (CLI, POST /reinforce, and the engram_reinforce MCP tool) confirms which source answered a query correctly, and similar future queries rank it higher. Bounded, inspectable, re-orders relevant results only — never resurrects non-matches. Pairs with the new self-evolve skill: observe the run → distill lessons → remember → reinforce → recall. See CHANGELOG.md.