workflow: retire todo label — unlabelled IS the default bucket

`todo` and `feature` were semantically near-identical ("do it, no
spec needed") and the boss-pickup decision treated both the same.
Collapsing the larger one into "no label" cuts the tag-noise on
16 of 24 issues; the 3 `feature` issues retain the label as a
deliberate "substantive but no full spec" marker against the
unlabelled bucket of mechanical follow-ups.

Label `todo` deleted in Gitea (Tea removed it from the 16
issues automatically). Remaining labels: `milestone`, `feature`,
`idea`, `in-progress`.

In-tree changes:

- CLAUDE.md: Gitea-issues bullet describes the new shape —
  three semantic labels + unlabelled-default-bucket.
- skills/boss/SKILL.md: Step 1 filter-snippet and direction-
  freedom commentary updated.
- skills/brainstorm/SKILL.md: Step 7.5 tea-create template
  drops `todo` from the choice set and notes that omitting
  `--labels` is the default-bucket path.

Verification: cargo test --workspace 647/0/2, architect_sweeps
exit 0, zero residual `todo`-as-label refs in live docs.

CLAUDE.md

@@ -226,16 +226,18 @@ not retroactively renamed.
 - **Gitea issues** (since 2026-05-20) are the forward queue —
   milestones, features, todos, and ideas. Browse:
   http://192.168.178.103:3000/Brummel/AILang/issues. CLI: `tea
-  issues ls --repo Brummel/AILang`. Labels: `milestone`,
-  `feature`, `todo`, `idea` (semantic class) and `in-progress`
-  (work has started). Big chunks that get their own
-  `docs/specs/` entry live as Gitea **milestones** (containers);
-  smaller items are standalone issues. No formal priority axis —
-  "what's next" is an orchestrator judgement call per session,
-  not a pre-set label. `idea` is the "may be cut" marker. The
-  orchestrator owns the backlog: opening new issues, retagging,
-  closing on completion (typically via the `closes #N` commit-
-  body trailer).
+  issues ls --repo Brummel/AILang`. Labels: `milestone` (needs a
+  `docs/specs/` entry, bounces back to the user in /boss),
+  `feature` (substantive addition, no full spec), `idea` (may be
+  cut, no commitment), `in-progress` (work has started). An
+  unlabelled issue is the default: a concrete task to just do,
+  no spec needed. Big chunks live as Gitea **milestones**
+  (containers); smaller items are standalone issues. No formal
+  priority axis — "what's next" is an orchestrator judgement
+  call per session, not a pre-set label. The orchestrator owns
+  the backlog: opening new issues, retagging, closing on
+  completion (typically via the `closes #N` commit-body
+  trailer).
 
 - **`docs/specs/<milestone>.md`** (since 2026-05-09): per-milestone
   design spec produced by `skills/brainstorm`. Hard-gate before any