📝 Document GitHub Flow branching model and agent task workflow

Adopt single-developer GitHub Flow: branches off main with a
feature/fix/chore prefix, merged back via 'git merge --no-ff' (local
PR). Releases are not triggered by pushes; only the maintainer runs
'npm run release', which tags and pushes; CI publishes to npm on the
tag. Gitea is the lab; GitHub is reserved for later promotion.

Replace the 'not yet settled' backlog note in AGENTS.md with concrete
agent instructions: a task with subtasks gets a branch, a leaf task is
worked on the current branch, and a fixed handover template (Implemented
/ Judgement calls / Known problems) frames the pre-merge review. Drop
the stale 'MR' reference in 'Never do' (no MR workflow). Update the
feedback-tier table and publishing workflow to gate CI on push to main,
not PRs. Check off the branching-model backlog group and open a task
for the release CI workflow (blocked on a missing Gitea runner).

backlog.tasks

@@ -5,12 +5,12 @@ Backlog and tracking for tiny-pattern-ts. Managed in vscode-todotasks format.
 ---
 
 Setup:
-☐ Add gitea actions, blocked by missing runner => pi --session 01a06e72-e61e-7327-b3e9-3e11749a523f @high
+☐ Establish release CI workflow: post-tag checks + npm publish after release tag push => pi --session 01a06e72-e61e-7327-b3e9-3e11749a523f @high
 ☐ Add gitea release page in CI @high
 ☐ Split off template into separate package => pi --session 01a07dde-7050-7054-bb36-1606d7eb2bc3 @high
-☐ Document branching model @critical
-    ☐ Describe branching model: when to branch, base branch, naming
-    ☐ Clarify release workflow: who pushes `main`, CI as post-merge gate, drop PR usage
+✔ Document branching model @done
+    ✔ Describe branching model: when to branch, base branch, naming
+    ✔ Clarify release workflow: who pushes `main`, CI as post-merge gate, drop PR usage
 
 v1.0:
 ☐ API surface is stable and fully typed