feat: local issue cache and draft-then-push workflow

Replace fetch_issue.py with four scripts around a flat, greppable cache in
tmp/issues/. Planning stays offline and issues reach Gitea in one push:

- issue_get.py: fetch by key or by filter (--milestone/--label/-q). The list
  endpoint carries issue bodies, so a whole milestone costs one request per 50
  issues. Gitea silently ignores an unresolvable milestones= filter and returns
  the entire backlog, so the milestone is resolved up front and every returned
  issue is re-checked locally. --deps walks the dependency graph downwards via
  the structured sections plus native dependencies and writes tree-<slug>.md.
- issue_push.py: validate a local draft against the canonical format, create
  missing labels with the right colors and exclusivity, POST, delete the draft.
- issue_list.py: discovery to stdout, writes nothing.
- issue_index.py: rebuild INDEX.md from what is on disk.

Files use one metadata field per line with inline lists so plain grep works
without a parser. This is a cache and a drafting area, not a mirror: no drift
tracking, no sync back.

Projects are not fetchable — the projects API is 404 on Gitea 1.26; documented
alongside the milestone caveat.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "tea",
-  "description": "Gitea CLI (tea) reference plus a mandatory-login guard. Ships /tea:auth (pin a login), /tea:use (command reference), /tea:issue (create issues in a canonical format), and a PreToolUse hook that blocks any tea command that would touch Gitea without --login.",
-  "version": "1.1.0",
+  "description": "Gitea CLI (tea) reference plus a mandatory-login guard. Ships /tea:auth (pin a login), /tea:use (command reference), /tea:issue (draft and push issues in a canonical format), scripts that keep issues in a flat greppable local cache, and a PreToolUse hook that blocks any tea command that would touch Gitea without --login.",
+  "version": "1.2.0",
   "author": {
     "name": "naudachu"
   },