one door for a request's purpose and role: purpose at the client, lane.Role on the calllog record (#928), prefix variance removed at source #1009

Why

#996 closed the auxiliary inventory one package deep. Its review (five passes, 2026-09-12) found the shape stops short in three places that are each a cross-package change and belong together as one wave, with #928 as the spine:

1. Purpose is a precondition of the wire, not a package convention. provider.NewClient (or the one place calllog.Record is written) takes the purpose and refuses/loudly flags an anonymous row. Deletes withPurpose, the inherited-blank exemption, the own-client second pass in internal/session, and covers internal/reflex, internal/head, internal/exec, internal/revision, internal/plan and cmd/aforge, which today spell provider.WithCallTag by hand and are invisible to internal/session's package-local law. The law becomes "no provider.NewClient outside the dispatcher without a purpose", module-wide.
2. lane.Role rides on the record (provider.WithCallRole beside WithCallTag), so cmd/aforge-replay's roleOf table is deleted rather than grown, the vision/spellout rows stop being hand-priced, and the standing check's tag reverts from standing-check to its role's own word sentinel (three packages spell "sentinel" for three things today; the join fixes that, not a rename).
3. Remove the prefix variance instead of measuring around it: one grep description everywhere (the "ripgrep absent" fact delivered at runtime in the tool result or one caps line), load_capability names what the build COULD have, so the fixed prefix is one number on every machine and widestBelt / WidestGrepDescription / the members seam in internal/exec/bare are deleted. Owner of bare's grep-description law must be in the room: that file states the two facts must be told up front.

Acceptance

End-to-end first: aforge chat --once on deepseek/deepseek-v4-flash with the guard, then ~/.aforge/logs/calls.jsonl shows every row with a purpose AND a lane role, including rows from the resident's quorum errand and a reflex call; cmd/aforge-replay prices them with no table. Unit: the module-wide go/ast law; the prefix gate's number identical on macOS with ripgrep+ffmpeg and on the Linux runner without either.

Measurements that make the case are in #996's PR body and PERF.md's prefix section.

Drafted with CodeAF · reviewed and owned by the author