chore: adopt trunk-based development with tbdflow

Adds .tbdflow.yml, .dod.yml, a Commit lint CI check, and workflow docs.

Author: ajsb85

.dod.yml

@@ -0,0 +1,8 @@
+# Definition of Done, shown by `tbdflow commit` before each commit.
+checklist:
+  - "`dart format .` produces no changes."
+  - "`dart analyze` reports no issues."
+  - "`dart test` passes."
+  - "New behaviour is covered by tests (golden vectors for codec changes)."
+  - "CHANGELOG.md is updated for user-visible changes."
+  - "The package still conforms to the firechip/cobs-conformance vectors."

.github/workflows/commit-lint.yml

@@ -0,0 +1,39 @@
+name: Commit lint
+
+on:
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  conventional-commits:
+    name: Conventional Commits
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Check commit subjects follow Conventional Commits
+        env:
+          BASE: ${{ github.event.pull_request.base.sha }}
+          HEAD: ${{ github.event.pull_request.head.sha }}
+        run: |
+          types='build|chore|ci|docs|feat|fix|perf|refactor|revert|style|test'
+          pattern="^(${types})(\([a-z0-9._/-]+\))?!?: .+"
+          fail=0
+          for sha in $(git rev-list --no-merges "$BASE..$HEAD"); do
+            subject=$(git log -1 --format=%s "$sha")
+            if printf '%s' "$subject" | grep -qE "$pattern"; then
+              echo "ok:   $subject"
+            else
+              echo "::error::Not a Conventional Commit: $subject"
+              fail=1
+            fi
+          done
+          if [ "$fail" -ne 0 ]; then
+            echo "Commit subjects must be Conventional Commits: type(scope): subject"
+            echo "Allowed types: ${types//|/, }"
+            exit 1
+          fi

.tbdflow.yml

@@ -0,0 +1,70 @@
+main_branch_name: main
+release_url_template: https://github.com/firechip/cobs_codec/releases/tag/{{version}}
+stale_branch_threshold_days: 1
+monorepo:
+  enabled: false
+  project_dirs: []
+issue_handling:
+  strategy: branch-name
+review:
+  enabled: false
+  default_reviewers: []
+  strategy: github-issue
+  workflow: null
+  rules: []
+  labels:
+    pending: review-pending
+    concern: review-concern
+    accepted: review-accepted
+    dismissed: review-dismissed
+  concern_blocks_status: false
+radar:
+  enabled: false
+  level: file
+  on_sync: true
+  on_commit: off
+  ignore_patterns:
+  - '*.lock'
+  - '*-lock.*'
+  - CHANGELOG.md
+ci_check:
+  enabled: false
+branch_types:
+  fix: fix/
+  refactor: refactor/
+  feature: feature_
+  ci: ci/
+  release: release_
+  docs: docs/
+  chore: chore/
+  feat: feat/
+automatic_tags:
+  release_prefix: v
+lint:
+  conventional_commit_type:
+    enabled: true
+    allowed_types:
+    - build
+    - chore
+    - ci
+    - docs
+    - feat
+    - fix
+    - perf
+    - refactor
+    - revert
+    - style
+    - test
+  issue_key_missing:
+    enabled: false
+    pattern: ^[A-Z]+-\d+$
+  scope:
+    enabled: true
+    enforce_lowercase: true
+  subject_line_rules:
+    max_length: 72
+    enforce_lowercase: true
+    no_period: true
+  body_line_rules:
+    max_line_length: 80
+    leading_blank: true

CONTRIBUTING.md

@@ -62,15 +62,49 @@ non-negotiable:
 - Keep the public surface minimal; add internal code under `lib/src/` and export
   deliberately from `lib/cobs_codec.dart`.
 
-## Commits and pull requests
-
-- Write clear, imperative commit messages (e.g. "Fix decoder backpressure on
-  delimiter-less runs").
-- Commits and tags in this repository are **SSH-signed**; please sign your
-  commits (`git config gpg.format ssh` and set `user.signingkey`) and include a
-  sign-off (`git commit -s`) certifying the [DCO](https://developercertificate.org/).
-- Keep pull requests focused; update `CHANGELOG.md` under an `## Unreleased`
-  heading for user-visible changes.
+## Git workflow: Trunk-Based Development with tbdflow
+
+This project uses [Trunk-Based Development](https://trunkbaseddevelopment.com/):
+small, frequent changes integrated into `main` (the trunk) rather than
+long-lived branches. We use the [`tbdflow`](https://github.com/cladam/tbdflow)
+CLI (`cargo install tbdflow`) so the safe path is the easy path.
+
+`tbdflow commit` pulls `main`, creates a Conventional Commit, and pushes:
+
+```console
+tbdflow commit --type fix --scope decoder -m "handle backpressure on idle links"
+```
+
+For a change that needs review, use a short-lived branch and merge it back
+quickly: `tbdflow branch --type feat --name my-change`, then `tbdflow complete`.
+Other helpers: `tbdflow sync`, `tbdflow radar`, `tbdflow changelog`,
+`tbdflow undo`.
+
+Two committed files drive this workflow:
+
+- **`.tbdflow.yml`** -- workflow + commit-message lint rules (trunk branch,
+  allowed Conventional Commit types, lowercase scope/subject, 72-char subject).
+- **`.dod.yml`** -- the Definition of Done checklist shown before each commit
+  (format, analyze, test, changelog, conformance). Bypass for a trivial change
+  with `--no-verify`.
+
+Commits and tags are **SSH-signed** (`tbdflow commit` respects the repo's
+signing config); include a sign-off (`-s`) certifying the
+[DCO](https://developercertificate.org/). Keep pull requests focused and update
+`CHANGELOG.md` under an `## Unreleased` heading for user-visible changes.
+
+## Conventional Commits
+
+Every commit message follows
+[Conventional Commits](https://www.conventionalcommits.org):
+`type(scope): short imperative subject`. Allowed **types**: `build`, `chore`,
+`ci`, `docs`, `feat`, `fix`, `perf`, `refactor`, `revert`, `style`, `test`. The
+subject is lowercase, imperative, and has no trailing period; breaking changes
+use `!` (`feat!:`) or a `BREAKING CHANGE:` footer.
+
+This is enforced locally by `tbdflow commit` and in CI by the **Commit lint**
+workflow (`.github/workflows/commit-lint.yml`), which checks every commit in a
+pull request.
 
 ## Reporting bugs