release: v1.23.1 — promote dev to main (catch-up)

[misnaej]

Promotes dev → main via the release/v1.23.1 branch (never a direct dev merge). main: 1.21.0 → 1.23.1.

Lumped catch-up (v1.22.0 + v1.23.0 + v1.23.1 in one): per-minor staged promotion was impossible for this batch because the #43 guard regression blocked promoting any minor below the global-max tag. #49 fixes that going forward; this PR carries #49's fix, so it passes cleanly (the guard skips — HEAD's tree reproduces the v1.23.1 tag).

Merge strategy: squash-and-merge — one release commit on main. Squash message posted as a comment below.

Included (1.21.0 → 1.23.1)

47dc0ae fix(promote): guard checks any tagged-release tree; add release-process spec (#49)
1aa0767 feat(config): forge-config advisor, layout config, forge:test skill (#45)
8ba47e9 fix(guards): align block_protected_branches default and tag resolver + CHANGELOG (#43)
4e11273 fix(promote): --promotion-status filters to X.Y.0 tags only (#40)

After merge

• main now == dev (v1.23.1); forge-next-prep --promotion-status should report 'Up to date'.
• Confirm/handle the v1.23.1 tag on main's squash commit per release-process.md §2.

[misnaej]

Squash-merge message — copy verbatim into the GitHub "Squash and merge" dialog:

release: v1.23.1 — promote dev to main (catch-up)

## Features
- forge-config --list advisor + repo-wide [tool.forge].source_dirs/test_dirs layout; docs/configuration.md; keep [tool.interrogate] native (#45)
- forge:test skill chaining the test agents (#45)

## Fixes
- Rolling-next guard recognizes any tagged-release tree — unblocks staged promotion of minors below the global-max tag (#49)
- block_protected_branches defaults dev_branch to "dev"; verify_plugin_version uses global semver-max tag resolution (#43)
- --promotion-status lists minors only, not patch tags (#40)

## Docs
- docs/release-process.md: single source of truth for versioning + promotion + invariant→test contract (#49)
- CHANGELOG.md with consumer upgrade-notes lane (#43)