D718 — Commits carry an Agent: trailer naming the calling MCP client

Decision. gitWrap appends Agent: <clientInfo name> to the commit of every agent-driven write, in one trailer paragraph after Reason: and before the Accepted-Finding: lines. changes_since returns the distinct agents per concept (agents) and, for a caller who sees the whole KB, commits_by_agent; concept_history returns agent per revision.

Why. Several agent clients of one user share one git author (and one token), so history could not say which client wrote what; the per-token author (#594) only separates agents that hold a token each. The MCP clientInfo name is already on the request context (the doctor nudge reads it), so the trailer costs no new protocol surface. Only the name is stored: the client is the grouping key, a version per commit is noise.

Alternatives rejected. - Storing name and version: noise in every commit and a key that splits on every client upgrade. - An unknown placeholder when the client did not identify itself: absence is honest and keeps old and new commits alike. - A new changes_since parameter to group by agent: the additive fields cost nothing to callers that ignore them. - The audit log or log.md: the first is a leakage allow-list, the second the curated narrative (same reasoning as D272).

Consequences. The name is self-declared by the client: the trailer is an attribution hint, never an identity; the authenticated identity stays the git author. The name is client-controlled text going into a commit message, so whitespace (newlines included) is collapsed and the value cut at 64 bytes on a rune boundary; without that a name could forge a Reason: or Accepted-Finding: trailer. Server-originated commits (external changes, auto-repair) carry no Agent:. In gitx the Reason field must stay last in the --pretty formats. commits_by_agent is filled only under WholeVisible, like commit_count. Builds on D272, D350 and #594.