Adopts ex_quality 0.14.0 format check-mode

[johnnyt]

Why

The fleet-wide format ruling (deciding bead sui-b5y in statifier-ui,
design PLAN-format-check-mode.md in ex_quality, operator-confirmed
2026-08-22) moves every repo's Format stage from rewrite mode to check
mode, so the quality gate reports unformatted files instead of silently
rewriting code during a gate run.

What

• Bumps the :ex_quality dev dependency ~> 0.13 -> ~> 0.14
  (0.14.0 is the release that ships check mode).
• Sets format: [check: true] in .quality.exs - the only change to
  that file.
• Adds the ADR-0011 ledger entry in docs/quality-gate-changes.md
  recording the operator ruling behind the .quality.exs and mix.exs
  edits.
• Updates CLAUDE.md's Build & Test guidance: the gate no longer formats
  for you - run mix format before committing. The dep-synced ExQuality
  block makes no auto-format claim and is untouched; no
  .claude/wurk/*.md file echoed the old guidance.

The tree was verified fully formatted before the flip, so this lands as
a single pure-config commit with no formatting commit ahead of it.

Notes

• mix gate.verify full green ("Full gate green: scope all, no
  profile, 13 stages considered"), with the Format stage reporting
  files_needing_format: 0 in check mode.
• mix quality --profile merge green; the ADR judge skipped cleanly
  (no files in the diff are in a judged ADR scope).
• Check-mode red verified locally: a deliberately unformatted file
  turns the gate red (Format: 1 file needs formatting) and the gate
  rewrites nothing; reverted afterward. CI runs mix gate.verify, so
  the same check applies there.
• Internal tooling only - no changelog fragment.

Closes st-k7pm