Default version.preset ("conventional") can't be loaded; a bad preset crashes release/standing-pr with an unhandled rejection and no envelope #652

Problem

1. The default preset doesn't exist. version.preset defaults to "conventional" (packages/config/src/schema.ts:92, packages/version/src/types.ts:220,231). The preset loader prefixes it to conventional-changelog-conventional, which isn't on npm (404). So every config without an explicit version.preset — including the one releasekit init writes, and repos with no config file — fails whenever the bump is inferred from commits (only --bump escapes it). The repo's own config pins angular, and every integration/e2e test pins angular or conventionalcommits, so nothing exercises the default.
2. An unloadable preset crashes the CLI on tagged repos. Bumper.loadPreset() (packages/version/src/core/versionCalculator.ts:386) starts the preset import() without a handler; the following await refExists(latestTag, …) (line 393) yields, the import rejects, and Node's default --unhandled-rejections=throw kills the process before the surrounding try/catch runs. release --json [--output] and standing-pr update --json --output exit 1 with no envelope (stdout empty, no --output file) — breaking the feat(cli): uniform JSON envelope with structured errors and changed reporting #608 envelope contract. On untagged repos the && short-circuits, the error is caught, and a GENERAL_ERROR envelope is written — still exit 1, not a config error.
3. The docs disagree on the default: "conventional" (docs/configuration.md, docs/migration.md, packages/config/README.md), "conventionalcommits" (packages/version/README.md, docs/troubleshooting.md), plus dead fallbacks 'conventional-commits' (versionEngine.ts:89-91) and 'angular' (versionCalculator.ts:146).

Regression note: the crash (as opposed to a clean failure) dates from 4431910 (#437, v0.33.0), which made refExists async; the default preset itself was never loadable.

Reproduction (built CLI, Node 22)

git init -q demo && cd demo && git config user.email t@e && git config user.name t
echo '{"name":"demo-pkg","version":"1.0.0"}' > package.json
echo '{"version":{}}' > releasekit.config.json      # or no config, "conventional", or "nonsense"
git add -A && git commit -qm "chore: init" && git tag v1.0.0
echo x > a.txt && git add -A && git commit -qm "feat: add a"
releasekit release --json --dry-run --output out.json; echo "exit=$?"; ls out.json

Exit 1, empty stdout, no out.json; stderr ends in an uncaught Unable to load the "conventional" preset (ERR_MODULE_NOT_FOUND: conventional-changelog-conventional) with a Node crash footer. angular / conventionalcommits work. conventional-commits works in flat npm/pnpm installs (hoisted alias from @releasekit/version) but not from the bundled packages/release/dist CLI the GitHub Action runs, because the preset loader is bundled into release's dist and import() resolves from there (NODE_PATH doesn't apply to ESM).

Impact

• New users following getting-started (releasekit init, then a release) fail on every commit-inferred release; after their first tag it's a raw crash with a bundled-code stack.
• In CI, release / standing-pr update exit 1 with no envelope, so the standing PR is never created or updated; the Action's summary says only "Release Failed", with the cause buried in the log.
• A typo'd preset fails the same way, and even the handled path reports GENERAL_ERROR (exit 1) rather than CONFIG_ERROR (exit 2).

Proposed fix

1. Loadable default: default to conventionalcommits; normalise conventional and conventional-commits to it (nobody's behaviour changes — conventional never loaded); regenerate the schema; drop the dead fallbacks.
2. Layout-independent loading: pass a loader to Bumper.loadPreset(preset, loader) that maps the supported names to static imports of conventional-changelog-angular / conventional-changelog-conventionalcommits (resolve any others via createRequire(projectDir) if custom presets are to be supported), then drop the conventional-changelog-conventional-commits alias dependency.
3. Validate at config load: an unknown preset throws ConfigError listing the supported names → exit 2 and a CONFIG_ERROR envelope.
4. Close the unhandled window: load the preset (awaited) inside the try before configuring the bumper — or at minimum do the refExists await before loadPreset — so nothing yields between starting the import and bump().
5. Docs: one stated default and supported list across configuration.md, migration.md, troubleshooting.md, and the version/config READMEs.

Acceptance criteria

• Tagged repo, no preset (or "conventional"): releasekit release --json --dry-run exits 0 with conventionalcommits rules — in npm, pnpm, and the GitHub Action (bundled release/dist) layouts.
• "preset": "nonsense", tagged and untagged: release and standing-pr update exit 2 with a CONFIG_ERROR envelope (stdout and --output) listing supported presets; a one-line stderr message; no crash footer.
• No unhandledRejection for any preset value under default Node settings.
• Tests: no-preset on a tagged repo (integration/e2e); unknown-preset config validation; CONFIG_ERROR envelope written to --output; an alias resolving from the bundled release CLI.
• Every doc names the same default.

Related: #544 (envelope contract), #616 (envelopes version/publish — coordinate the version path).