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/0004-issue-create-and-comment.md

@@ -0,0 +1,23 @@
+---
+spec: gitea-axi
+blocked-by: 0003-issue-view-and-truncation
+---
+
+## What to build
+
+The first mutations: `issue create` and `issue comment`, introducing the shared machinery for `--body-file`, name→ID resolution, and mutation output blocks.
+`issue create` takes `--title` (required), `--body`/`--body-file`, `--assignee`, repeatable `--label` (resolved to label ID via the case-insensitive label lookup), and `--milestone` (resolved via the milestone name query); `--project` and `--type` are excluded.
+Create output is the entity block `issue: { number, title, state, url }` with extra fields (`labels`, `assignees`, `milestone`, `body`) available via `--fields`.
+`issue comment <n>` requires `--body`/`--body-file` and returns the created comment directly from the POST response as `comment: { number, author, created, body }` with the body truncated at 800 chars — no follow-up view call needed; the comment's own id is not output.
+`issue comment` stays permissive toward PR numbers (PRs genuinely share the comment endpoint).
+
+## Acceptance criteria
+
+- [ ] `issue create --title` creates an issue and outputs `issue: { number, title, state, url }` where `url` is `html_url`
+- [ ] Missing `--title` fails immediately with `VALIDATION_ERROR` (exit 2) before any API call
+- [ ] `--body-file <path>` reads the body from a file; `--body` and `--body-file` together are rejected
+- [ ] `--label` resolves each name to an ID via case-insensitive lookup against the repo's labels; an unknown name yields `VALIDATION_ERROR`
+- [ ] `--milestone` resolves the name via the milestone query; an unknown name yields `VALIDATION_ERROR`
+- [ ] `issue comment <n> --body` posts and outputs `comment: { number, author, created, body }` built from the POST response, body cleaned and truncated at 800 chars, where `number` is the issue number
+- [ ] `issue comment` accepts a PR number without a type-guard error
+- [ ] Fixture-server tests cover create with labels/milestone, both body sources, comment output shape, and each validation failure