ci(pgtest): raise the job timeout to 30 minutes (RIG-5324)

[rigel-mintaka]

Summary

• Raise the pgtest job's timeout-minutes from 20 to 30.
• Successful pgtest jobs now take 17.7 to 19.4 minutes. The -race real-Postgres suite alone takes about 17 minutes, and the sqlc-vet bootstrap runs after it.
• Two recent jobs were cancelled at 20.2 and 20.4 minutes. In the ci(sql-migration-gate): re-enable migration-immutability after the 0001 collapse (RIG-4897) #2244 run, all 11 Postgres packages reported ok before the cancel landed during the sqlc-vet bootstrap. Thirty minutes gives about ten minutes of headroom over the slowest passing run.

Verification

• actionlint .github/workflows/ci.yml: clean.
• Durations come from the last 40 ci.yml runs (gh run view start and end times of the pgtest job).
• PR CI: 8 success, 10 skipped, rollup green. pgtest was skipped by its affected-path filter, so the new limit takes effect on the next Go/SQL PR.

Risks

A truly wedged job now holds a runner 10 minutes longer before it is cancelled. The per-package go test -timeout 15m still panics a stuck package first. Rollback is to revert this one line.

Compatibility

None: CI configuration only. The rollup still requires pgtest to succeed.

Documentation

None: docs/architecture/build-and-ci.md does not document the pgtest limit.

Ledger-impact: none (CI timeout only; no recorded decision covers it)

[trunk-io]

😎 This pull request was merged.

[linear-code]

RIG-5324

[rigel-mintaka]

Review at head 3103b90: high 0, medium 0, low 0. Earlier passes raised 4 low findings in total, all about wording in the comment and commit message. Each one is fixed: the last in additive commit 3103b90, which a confirmation pass reviewed as 0/0/0.

[github-actions]

Compass engineering docs preview: https://compass-native-rig-5324-pgte.compass-eng-docs.pages.dev

Deployed from compass-native/rig-5324-pgtest-timeout at 3103b90.