feat(discord): git verbs for the Discord Sage on the shared-signals root, seat identity through a package credential helper, vault record protocol (#1509)

Row 24. A writable root that is a git work tree may carry a git object in
the binding; the seat then has git_status, git_commit (explicit paths, seat
author, Requested-by trailer from the envelope requester, push at once per
D6), git_pull (ff-only) and git_push (one branch, never force), plus
reserve_id and per-write clone locks under protocol vault. Git children run
with no host config and one credential helper, bin/git-credential.mjs,
reading the 0600 seat token file named in the binding; the fleet helper
serves only the Gitea hosts. Suite 58/58, node 143. rev-code-02 APPROVED
round 1 (#1509 comment 26375, tree 82ab962f).

Co-Authored-By: Claude Fable 5.1 <[email protected]>

docs/plans/2026-09-16_discord-git-tools.md

@@ -19,9 +19,11 @@ fixed argument list, run only in a root that is marked `"write": true`
 and is a git work tree. No verb takes free-form arguments.
 
 - `git_status(root)`: branch, ahead/behind, changed paths. Read only.
-- `git_commit(root, message, paths?)`: stages the named paths (or every
-  change under the root when omitted), refuses a dot-prefixed path or a
-  path outside the root, refuses an empty message or one over 500
+- `git_commit(root, message, paths)`: stages exactly the named paths
+  (one to fifty; the "every change when omitted" form of the first draft
+  was dropped for section 6's explicit-path rule, since the root is
+  Jason's own clone), refuses a dot-prefixed path or a
+  path outside the root, refuses when the index already holds staged work, refuses an empty message or one over 500
   characters, refuses when nothing is staged, commits with author
   `Sage <[email protected]>` and a trailer naming the Discord author
   by role (`Requested-by: Jason` or `Carmen`, never an id). Returns the
@@ -38,18 +40,34 @@ the one the binding names (`"branch": "main"`), so a detached head or
 another branch refuses; 60 s timeout; stdout and stderr are captured,
 trimmed to 4 KiB and returned as data; exit codes become fixed refusals.
 
-Credentials: the connector already runs with `MOSAIC_AGENT_NAME=sage`.
-The engine adds `MOSAIC_GIT_IDENTITY=sage` to the child environment and
-the repository's existing helper (`git-credential-mosaic`) resolves the
-seat's GitHub token at push time. The token is never read, printed,
-journaled or passed as an argument; a push failure returns git's message
-with any `https://…@` form masked.
+Credentials, as built (2026-09-18; the draft above said the fleet helper
+would serve): `~/.mosaic/tools/git/git-credential-mosaic` answers only
+the two Gitea hosts and exits silently for github.com, and the host's
+global git config sends github.com to Jason's own `gh` login. Neither is
+acceptable for Sage, so the verbs run git with `GIT_CONFIG_GLOBAL=/dev/null`,
+`GIT_CONFIG_NOSYSTEM=1`, no askpass, no prompt, and one helper set
+through `GIT_CONFIG_COUNT`: the package's `bin/git-credential.mjs`,
+which answers `get` over https from the 0600 file the binding names in
+`tokenFile`. The connector checks the file's mode at load and never reads
+it; the path reaches git only for push, pull and reserve, through the
+environment, never as an argument. The token is never read by the
+connector, printed, journaled or passed as an argument; a push failure
+returns git's message with any `https://…@` form and token shape masked.
+The D5 identity (seat token, `Sage <[email protected]>`) is unchanged;
+only the mechanism that presents it differs from the draft.
 
-Binding (`tools` key, fixed):
+The requester in the trailer is the Discord author's server name, which
+the connector now writes into the envelope line (`requester="…"`) and the
+extension reads on `before_agent_start`. A turn without a requester
+cannot commit.
+
+Binding (`tools` key, fixed), as built:
 
 ```json
 { "name": "shared-signals", "path": "…/shared-signals", "write": true,
-  "git": { "branch": "main", "identity": "sage" } }
+  "git": { "branch": "main", "identity": "sage",
+           "tokenFile": "…/secrets/github-jetrich-sage.token",
+           "author": "Sage <[email protected]>", "protocol": "vault" } }
 ```
 
 Without `git` on a root, no git verbs are offered for it. The prompt