feat(board): derive board refs, PR gates and stacks from stored rows (RIG-5171)

[rigel-mintaka]

This PR is part of a stack containing 5 PRs:

1. main
2. feat(store): status board tables, patch merge and board reads (RIG-5170) #2212
3. feat(comms): carry an optional issue or PR ref on asks (RIG-5173) #2228
4. "feat(board): derive board refs, PR gates and stacks from stored rows (RIG-5171)" (this PR)
5. feat(mirror): mirror asks and topics to forge issues and PRs (RIG-5181) #2275
6. feat(board): agent board RPCs, roster summary and board events (RIG-5172) #2285

Summary

Status board T3: derive board refs, PR gates and stacks from stored rows, with no forge calls. It is stacked on T5 (#2228) and T2 (#2212).

• DeriveRefs resolves each task ref with one batched read per kind: PRs, issues, open authored refs, and authored coordinates.
  • GitHub owner/repo#N: a PR row wins, then an issue row.
  • Linear KEY-N maps to provider 4 / linear.app.
  • Unknown, number-0 or unconfigured refs are UNSPECIFIED, with no error.
  • owned comes from the authorship row regardless of forge state.
  • untracked_refs lists open authored artifacts that no task names, matched on the full coordinate plus kind.
  • observed_at_unix_ms comes from forge_updated_at.
• PrGate, first match wins: merged, closed, queued / queue-failed / queue-removed, draft, conflicts, checks failed or pending, changes requested, awaiting review, awaiting enqueue.
  • Latest decision per human author; commented reviews never replace a decision, and dismissed clears one.
  • Required checks are read first, then the roll-up. A missing or empty roll-up is pending.
  • An approval on an older commit is stale. An unresolved thread holds the PR at awaiting review.
• StackOf: bottom-up positions, and the PR with no child is the tip. At a fork, each leaf is a tip and a shared ancestor takes the lexically first leaf. DeriveRefs calls it per provider and host.
• Store:
  • Issue.ForgeUpdatedAt is threaded through every issue read.
  • New batched AuthoredCoordsForAgent query.

Not here:

• tracker_status stays empty; T12 adds its columns.
• Review commit_id and PR head_sha ingestion is T14 (RIG-5182, feat(forge): carry PR head SHA, mergeable state and review commit id (RIG-5182) #2194). Until that lands, approvals read as current.

Tests

• Unit tests:
  • PrGate: each gate, overlapping precedence cases, required check vs roll-up, latest decision per author with comment and dismissal, stale approval, unresolved thread.
  • StackOf: chain, fork, host and provider separation.
  • DeriveRefs with a recording fake: batching, unknown and number-0 refs, Linear and mixed-case GitHub coordinates, PR over issue at one coordinate, untracked suppression across host, provider and kind, owned for a merged PR.
• pgtest TestDeriveRefsFromStore runs on seeded rows, including issue observed_at.
• Store pgtest TestBoardCoordinateReadsAndOpenAuthoredRefs.
• Red checks were run on each regression fix.
• Gates: golangci-lint (with and without the pgtest tag), build, vet, sqlc-drift, inline-sql-gate, and the moon ci pre-push gate.

Refs RIG-5171

Ledger-impact: none

[linear-code]

RIG-5171

RIG-5173

[rigel-mintaka]

Review result: head ab9ea29

Review-lead fan-out (correctness, security, design, style).

Round	High	Medium	Low	Outcome
R1	0	4 accepted	4 accepted	fixed (number-0 refs, empty roll-up is pending, host-isolated stacks, precedence tests); commit_id/head_sha ingestion deferred to T14 (RIG-5182)
R2	1	2	3	fixed (commented reviews keep a decision, durable ownership, stack key isolation, all parseable refs suppress)
R3	0	1	1	fixed (untracked match on full coordinate plus kind; driver red-checked)
R4	0	1	2	fixed (GitHub refs suppress both PR and issue keys, independent subtest, test rename)
R5	0	2 (test gaps)	0	fixed (PR-over-issue precedence test, configured-host suppression test)

Dismissed with reasons: tracker_status (a later task adds its columns), per-ref recovery from corrupt stored rows (failing closed is intended), and the Linear fallback URL route (unspecified).

No open findings.

[github-actions]

Compass engineering docs preview: https://compass-server-rig-5171-boar.compass-eng-docs.pages.dev

Deployed from compass-server/rig-5171-board-derive at 0d78f52.

[rigel-mintaka]

Rebase note: restacked on #2228 (7ab717a8). Interdiff from reviewed head ab9ea29b to 1b9db2f3 is empty. Title fixed to RIG-5171; it had inherited #2228's.

[rigel-mintaka]

Rebase note: rebased onto main (b1e8515) after RIG-5326 and RIG-5324 landed. Interdiff from approved head 1b9db2f3 to 0d78f527 is empty.