Architecture reflex

Use architecture context only when it will eliminate the next broad source read.

1. If this repository has .archctx/architecture.json, run archctx status; if its local guidance names another config, use that exact path instead.
2. When it is FRESH, make one smallest query: search to locate a capability; canonical or
   evidence for a known component; trace only when the declared component relation is the
   question; changed-since or drift only with a supplied base revision.
3. Read only the returned source evidence needed for the task. Source wins over the index.

If the index is missing, stale, invalid, or does not reduce the next read, use ordinary targeted
discovery. Do not refresh merely to answer a read-only question, and never treat Archctx as a gate.