feat(discord): read-only tools for the Discord Sage through a Mosaic pi extension confined to declared roots (#1509)

A binding may declare `tools` with named roots. pi starts with
--no-builtin-tools and the package's own extension, allowlisting
list_dir, read_file and search. src/tools.mjs holds the rules: names
not paths, per-segment lstat walk, one checked descriptor read that
refuses symlinks, swaps, FIFOs, hard links and oversize files, credential
shapes refusing the whole read, and a per-message call budget. The engine
settles on agent_end and records tool calls in the turn record.

Jason's rulings R1-R7 in the brief, section 7. rev-code-02 approved
round 2 (comment 26276) on tree 43f0329b after four round 1 fixes.
Suite 48/48, node tests 116. Not pushed.

Co-Authored-By: Claude Opus 5 <[email protected]>

docs/plans/QUEUE.md

@@ -45,7 +45,7 @@ Gaps found while working go to `docs/plans/DEFERRED.md`, not here.
 | 18 | Control board row for the Discord connector (MVP iteration 3): discovery from binding files, liveness from run.lock, reply refused | darkwing (Jason's ruling 2026-09-13); coordinator answers connector-side questions | #1509 | briefed; assigned to darkwing, not started | a Sage (discord) row on the board shows live, offline and braked correctly, and reply from the board is refused | `2026-09-13_discord-connector-pilot.md` section 11 |
 | 19 | Discord connector: binding reload without a restart (`reload` verb, SIGHUP, `systemctl --user reload`); channels, users, limits and guildName apply in place, identity, engine and context stay fixed, an invalid file is refused and the old binding kept (MVP iteration 4) | coordinator | #1509 | done: caaef941; live 00:03 UTC: reload applied Carmen's entry with no restart, unknown key refused by the CLI (exit 2), fixed key refused in the process with the binding kept, `systemctl --user reload` applied; suite 41/41 (101 node tests); receipt `mvp4-5-reload-carmen-*.json` | edit the binding, run `scripts/discord.sh reload shared-signals`, the change applies with no restart, a broken edit is refused and journaled | `2026-09-13_discord-connector-pilot.md` section 11 |
 | 20 | Discord connector: per-user channel allowlist in the binding and Carmen enrolled (all listed rooms except #sage-admin) (MVP iteration 5) | coordinator | #1509 | done: caaef941 (`users[].channels` allowlist, `channel-not-for-user` drop); Carmen enrolled live by reload 00:03 UTC; her first message is the remaining check | Carmen gets a reply in #general and silence in #sage-admin; Jason unchanged | `2026-09-13_discord-connector-pilot.md` section 11 |
-| 21 | Discord connector: read-only tools for the Discord Sage through a Mosaic pi extension confined to declared roots (MVP iteration 6) | coordinator; reviewer per Q12 | #1509 | briefed; waiting on Jason's D1–D3 (roots, every listed user, Q16) | Sage answers a question from a file under a declared root with the reads in the turn record; a read outside the roots is refused and recorded | `2026-09-14_discord-readonly-tools.md` |
+| 21 | Discord connector: read-only tools for the Discord Sage through a Mosaic pi extension confined to declared roots (MVP iteration 6) | coordinator; reviewer per Q12 | #1509 | approved: rev-code-02 round 2 verdict 26276 (tree 43f0329b); committed locally; live check in #sage-admin with Jason next; Jason ruled R1–R7 2026-09-14 (roots docs/ and agents/sage/, Carmen included) | Sage answers a question from a file under a declared root with the reads in the turn record; a read outside the roots is refused and recorded | `2026-09-14_discord-readonly-tools.md` |
 
 Start message for row 6, sent from the board to darkwing:
 "Read docs/plans/QUEUE.md, then the plan page section "Piece 5: darkwing on
@@ -94,3 +94,4 @@ Gate F or when blocked."
 - 2026-09-13 — coordinator: rows 19 (binding reload) and 20 (per-user channels, Carmen) added on Jason's "proceed in order"; row 19 in progress. No other row changed.
 - 2026-09-13 — coordinator: rows 19–20 done (caaef941, live reload 00:03 UTC, Carmen enrolled); Carmen's first message pending as the operator check. No other row changed.
 - 2026-09-14 — coordinator: row 21 (read-only tools) briefed on Jason's "let's move to tools"; Carmen's test deferred by Jason; waiting on D1–D3 in the brief. No other row changed.
+- 2026-09-14 — coordinator: row 21 rulings in (brief section 7), built and approved by rev-code-02 (26276); suite 48/48, 116 node tests; committed locally, live check next. No other row changed.