feat(gitea): add 84 actions covering PRs, files, reviews and repository management (#248)

## Summary

Extends the Gitea provider from issues-only to broad repository
management coverage: **84 actions** spanning pull requests, reviews,
file contents, branches, commits, tags, releases, labels, milestones,
webhooks, collaborators, organizations, stars, deploy keys and
repository CRUD — so agents can drive a Gitea instance end to end.

## New actions (84 total)

**Pull requests (9)**
- `gitea.list_pull_requests`
- `gitea.get_pull_request`
- `gitea.create_pull_request`
- `gitea.update_pull_request`
- `gitea.update_pull_request_branch`
- `gitea.merge_pull_request`
- `gitea.check_pull_request_merged`
- `gitea.list_pull_request_commits`
- `gitea.list_pull_request_files`

**Pull request reviews (5)**
- `gitea.list_pull_request_reviews`
- `gitea.create_pull_request_review`
- `gitea.submit_pull_request_review`
- `gitea.dismiss_pull_request_review`
- `gitea.delete_pull_request_review`

**Reviewers (2)**
- `gitea.request_pull_request_reviewers`
- `gitea.remove_pull_request_reviewers`

**Review comments (1)**
- `gitea.list_pull_request_review_comments`

**Repository file contents (4)**
- `gitea.get_repository_contents`
- `gitea.create_file`
- `gitea.update_file`
- `gitea.delete_file`

**Branches & commits (7)**
- `gitea.list_branches`
- `gitea.get_branch`
- `gitea.create_branch`
- `gitea.delete_branch`
- `gitea.list_commits`
- `gitea.get_commit`
- `gitea.create_commit_status` / `gitea.list_commit_statuses`

**Tags & releases (7)**
- `gitea.list_tags`
- `gitea.get_tag`
- `gitea.create_tag`
- `gitea.delete_tag`
- `gitea.list_releases`
- `gitea.get_release`
- `gitea.create_release`
- `gitea.update_release`
- `gitea.delete_release`

**Labels & milestones (11)**
- `gitea.list_repository_labels`
- `gitea.get_label`
- `gitea.create_label`
- `gitea.update_label`
- `gitea.delete_label`
- `gitea.list_issue_labels`
- `gitea.add_issue_labels`
- `gitea.remove_issue_label`
- `gitea.replace_issue_labels`
- `gitea.clear_issue_labels`
- `gitea.list_milestones`
- `gitea.get_milestone`
- `gitea.create_milestone`
- `gitea.update_milestone`
- `gitea.delete_milestone`

**Webhooks (6)**
- `gitea.list_repository_hooks`
- `gitea.get_repository_hook`
- `gitea.create_repository_hook`
- `gitea.update_repository_hook`
- `gitea.delete_repository_hook`

**Collaborators & deploy keys (9)**
- `gitea.list_collaborators`
- `gitea.add_collaborator`
- `gitea.remove_collaborator`
- `gitea.get_collaborator_permission`
- `gitea.list_repository_keys`
- `gitea.get_repository_key`
- `gitea.create_repository_key`
- `gitea.delete_repository_key`

**Organizations (4)**
- `gitea.list_my_organizations`
- `gitea.get_organization`
- `gitea.list_organization_members`
- `gitea.list_organization_repositories`

**Stars & topics (5)**
- `gitea.list_repository_stargazers`
- `gitea.star_repository`
- `gitea.unstar_repository`
- `gitea.list_repository_topics`
- `gitea.update_repository_topics`

**Repository & misc (6)**
- `gitea.create_repository`
- `gitea.update_repository`
- `gitea.delete_repository`
- `gitea.fork_repository`
- `gitea.list_repository_watchers`
- `gitea.list_issue_assignees`

**Issues (extended, 9)**
- `gitea.list_repository_issues`
- `gitea.get_issue`
- `gitea.create_issue`
- `gitea.update_issue`
- `gitea.list_issue_comments`
- `gitea.create_issue_comment`
- `gitea.update_issue_comment`
- `gitea.delete_issue_comment`

**Existing (9, unchanged)**
- `gitea.get_current_user`
- `gitea.list_my_repositories`
- `gitea.get_repository`
- `gitea.search_repositories`

## Implementation notes

- All endpoints verified against the Gitea 1.26.4 OpenAPI spec.
- `create_file` / `update_file` base64-encode the `content` input
automatically before sending, using `Buffer` when available and a
`TextEncoder`/`btoa` fallback for Worker environments.
- Nested `filePath` values are encoded per-segment so paths like
`src/utils/helper.ts` survive URL construction.
- `merge_pull_request` sends the Gitea `Do` merge-style field and
returns `{ ok: true }` plus the raw response.
- Pagination honors the `x-total-count` header; list actions expose
`total_count`.
- Includes a smoke test suite (`src/providers/gitea/runtime.test.ts`, 35
tests).

## Checks

- `npm run typecheck` ✅
- `npm run lint` ✅ (0 warnings, 0 errors)
- `npm run format` ✅
- `npx vitest run` ✅ (638 tests passed)

---------

Co-authored-by: souloss <souloss@users.noreply.github.com>
Co-authored-by: Kevin Cui <bh@bugs.cc>

Author: souloss