docs: adopt Conventional Commits and land planning docs

- CONVENTIONAL-COMMITS.md: vendored spec (v1.0.0); CLAUDE.md requires
  agent-written commits to follow it
- tasks 0002-0020: remaining task breakdown of the gitea-axi spec
  (0019 reframed around the three-tier test taxonomy: unit,
  integration, end-to-end)
- spec, CONTEXT.md, and ADRs 0006/0007/0011: pending design
  refinements from the planning sessions

.claude/tasks/0015-label-commands.md

@@ -0,0 +1,22 @@
+---
+spec: gitea-axi
+blocked-by: 0004-issue-create-and-comment
+---
+
+## What to build
+
+The label command group: `label list`, `label create`, `label edit`, `label delete`.
+`label list` takes `--limit` (default 500) and outputs a count line plus `labels: [ { name } ]`.
+`label create` requires `--name` and `--color` (hex without `#`; the `#` is prepended before the API call) with optional `--description`; it is idempotent via a case-insensitive existence check, reporting `create: already_exists` instead of failing.
+`label edit <name>` and `label delete <name>` resolve the positional name via the standard case-insensitive label lookup with `VALIDATION_ERROR` when not found.
+`label delete` is deliberately not idempotent — a nonexistent label is refused rather than reported as success (see ADR 0010).
+
+## Acceptance criteria
+
+- [ ] `label list` renders the count line and `labels:` block; empty repos get the explicit empty state
+- [ ] `label create --name --color` creates the label, prepending `#` to the color, and outputs `created: ok` + `label: <name>`
+- [ ] Creating an existing label (case-insensitive) outputs `create: already_exists` + the existing name, exit 0
+- [ ] `label edit <name>` applies `--name`/`--color`/`--description` and outputs `edit: ok` + the resulting name
+- [ ] `label edit`/`label delete` on an unknown name yield `VALIDATION_ERROR` (exit 2)
+- [ ] `label delete <name>` outputs `delete: ok` + `label: <name>`
+- [ ] Fixture-server tests cover create, idempotent re-create, edit, delete, and the unknown-name refusals