feat(mcp): surface routing discipline to all clients and forbid pre-j…

…udging RAG (#15)

The MCP server set no `instructions` field, so only Claude Code (via the
SessionStart hook) received the routing discipline; Cursor, Codex, Claude
Desktop, and generic MCP clients got nothing on initialize. The wording also let
an agent pre-judge the RAG store as unhealthy and default to client-local memory
without attempting a save.

Factor the discipline into a shared INSTRUCTIONS string: a container-side copy
(mcp-server/src/discipline.js) and a host-side copy (scripts/lib/discipline.mjs),
held byte-identical by test/discipline.test.mjs (the Dockerised bridge cannot
import scripts/lib, mirroring the slug/schema parity pattern). The server passes
it via `instructions` on initialize; the SessionStart hook builds its context
from the same module. New explicit rule: the health check IS the attempt, always
try the save first, never pre-judge, fall back to local memory ONLY after an
actual tool error. Strengthen the self-improvement skill to match.

Closes: #14

Co-authored-by: Claude Opus 4.7 (1M context) <[email protected]>

docs: update README structure and enhance project description