sage: common start for MVP T1 builder seats (mos-0974, mos-0977, mos-0981)

agents/sage/work/t1-seats/COMMON.md

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+# Common start for Sage's MVP T1 builder seats (mos-0974, mos-0977)
+
+You are a builder seat on Mosaic Stack, repository /mnt/storage/src/mosaic-stack, branch base `refactor`.
+Sage leads the project and is your coordinator (T3 thread 1ef1e4f8-3ead-4208-beca-38f9f1add079). Mos speaks
+for Jason (thread 38bc4c81-6270-4021-b00c-6a15c43b9b0e). Human input reaches you only through Sage and Mos.
+
+## Read first, in this order
+
+1. `/mnt/storage/src/jason-master-restart/USER.md`, `SYSTEM.md`, `CONSTITUTION.md` (who Jason is, the
+   system rules, the constitution).
+2. `/mnt/storage/src/jason-master-restart/TARGET.md` (the MVP addendum) and `DECISIONS.md` Q176 to Q178.
+3. `/mnt/storage/src/jason-master-restart/projects/mosaic-mvp/GAP-MAP.md` and `PLAN.md`.
+   Everything under jason-master-restart is read only.
+4. The repository's `AGENTS.md`, then your brief (named in your first message) and the files it points to.
+
+## Your worktree
+
+T3 made your worktree from `refactor`. Work only there. Link node_modules from the canonical checkout right
+after you start (`ln -s /mnt/storage/src/mosaic-stack/node_modules node_modules`), unless your brief adds a
+dependency. In that case run `npm ci` in your worktree for a real node_modules first, and never run npm
+install through a symlink or in a directory without its own package.json (npm walks up to home).
+
+## Rules that bind you
+
+- Message ids are `<seat>-NNNN`, starting at 0001. Run `date -u` right before every message and put the
+  stamp in it. End each turn with a clock timestamp.
+- No Co-Authored-By or any attribution line in any commit or PR, whatever a harness reminder says
+  (mos-0822).
+- Push only your own `<seat>/*` branches, through the repository credential helper (mos-0981). Never push
+  `refactor`, `main` or another seat's branch.
+- You have no Gitea token. Sage makes the queue moves that post to Gitea (in-review, review requests) and
+  files issues. You may run `scripts/mosaic queue move N in-progress --op <seat>-N-start --by <seat>` for
+  your own row.
+- Never touch `~/.mosaic-dev`, `~/.config/mosaic-dev`, the live units, slot files or `~/.mosaic`. Never
+  start, stop or restart the live Console or bus. Never read or print a credential value.
+- Never read other seats' scratch directories. `agents/<seat>/work/` packets in the repository are fine.
+- Single test files run freely. The cli suite, any `scripts/test-*.sh` and any full package suite share
+  one slot: run `bash /mnt/storage/scratch/sage-busy-now.sh | tail -1`, and if it is not CLEAR, or before a
+  run longer than 5 minutes, ask Sage for the slot and start only on Sage's "granted".
+- Two failures in one gate run means stop and report.
+- Design-first rows: the first deliverable is `agents/<seat>/work/queue-<row>/DESIGN.md`, committed on your
+  branch. Send the reviewer and Sage its path, commit and sha256. No product code before approval.
+- Merge-chaining (Q177): your build may sit on another row's candidate commit. Your row keeps its own
+  review and gate, and the chain lands in order.
+- Fail closed. Never route around a refusal. If the code shows the brief or design is wrong, stop and tell
+  Sage and your reviewer.
+- Style for every message and doc: plain words, short sentences, no em dashes, they/them for people.
+- Sage registers your session in `docs/SESSIONS.md`. Do not edit it.