Cardano Updates

## Summary

- Add `--quiet` to every `nix build`, `nix shell`, `nix run`, `nix
develop`, and `nix flake` invocation across all 11 CI workflow files
- Replace `-L` (verbose log) and `--log-format raw-with-logs` with
`--quiet`
- Add `--quiet` to nix commands inside CI scripts (`scripts/ci/`) and
run helpers (`run/`)
- Remove xtrace (`set -euox` → `set -euo`) from 7 CI and run scripts
- Add "Nix verbosity" convention section to CI contributor docs

## Commits

1. **`--quiet` in workflows** — 11 workflow files + docs (26 files
total)
2. **`--quiet` in scripts** — 9 CI/run scripts with nix commands
3. **remove xtrace** — 7 scripts with `set -euox` → `set -euo`

## Verification

```
grep -rn -E '\bnix (build|shell|run|develop|flake)\b' .github/workflows/ scripts/ run/ | grep -v -- '--quiet' | grep -v '^#'
```
returns only shebang comments — all active nix commands have `--quiet`.

```
grep -rn 'set -.*x' scripts/ run/ | grep -v '^#' | grep -v interactive-print
```
returns only commented-out lines.

Closes #5148, closes #5118

Remove xtrace (`set -euox` → `set -euo`) from docker and nix run
scripts to reduce CI log noise. Also add --quiet to nix shell
invocations in the run helper scripts.

Replace -L with --quiet and add --quiet where missing across all
CI workflow files. This suppresses verbose nix build logs and
warnings that clutter GHA output.

Closes #5148, closes #5118

ruby-e2e.sh no longer contains a version string, so the sed
replacement is a no-op and git commit fails with "nothing to commit".
Use git diff --quiet to skip commits when there are no changes.

runPeer and Stateful.runPeer now require MonadEvaluate m
after the ouroboros-network bump in cardano-node 10.5.4.
MonadEvaluate implies MonadThrow and MonadMask, so those
become redundant.

Also fix: redundant mapMaybe import in FlakyTests.GHA.

Closes #5172

## Summary

- Rewrite `updating-dependencies.md`: replace stale Jörmungandr /
`./nix/regenerate.sh` / Buildkite references with cardano-node bump,
CHaP-only bump, and GHC bump sections (sourced from
`.claude/skills/cardano-deps/SKILL.md`)
- Add fourmolu migration ADR (`2026-02-12-fourmolu-migration.md`)
- Replace stylish-haskell with fourmolu in `coding-standards.md` and
`building.md`
- Mark 2023-01-27 CI decision as superseded by 2026-02-10 GHA migration
- Add PR references (#5105, #5124, #5149, #5153, #5168) to GHA migration
ADR
- Add missing entries to `SUMMARY.md`

Closes #5173, closes #5174

Closes #5175

## Summary

- Add `concurrency` groups with `cancel-in-progress: true` to 5
workflows that were missing them: `lean.yml`, `linux-e2e.yml`,
`linux-mithril-sync.yml`, `publish.yml`, `windows-tls-diagnostic.yml`
- Bump Mithril sync timeout from 2.5h to 4h (job: 150→250 min, script:
7200→14400 sec)

Closes #5171
Closes #5176

Closes #5171
Closes #5176

Closes #5172

runPeer and Stateful.runPeer now require MonadEvaluate m
after the ouroboros-network bump in cardano-node 10.5.4.