fix(ci): delete the per-branch push triggers instead of adding feat/** to them

The tracked next-step said "align gate.yml's push trigger with this repo's feat/**
prefix". Doing that literally would have made things worse, so this does the opposite.

act_runner runs at capacity 1. A branch push and its PR fire the SAME gate over the SAME
tree, and the redundant run SERIALISES AHEAD of the PR run -- doubling the wall clock on
the one result that gates the merge. Adding another prefix widens that, it does not fix
it. infra/plex/claim-ship.sh currently has to pick a feat/ branch name specifically to
DODGE this, during a loop that is racing a short-lived token.

The prefix list also silently failed to match this repo's own convention: branches here
are feat/**, which was absent, so the "fast feedback" never fired for the most common
prefix. Nobody noticed for a month because the only symptom of a wrong entry is a MISSING
run. Any hand-maintained prefix list has that failure mode. Deleting the list removes the
whole class rather than correcting one entry.

It was redundant anyway: CLAUDE.md already requires ./ci/gate.sh in the pinned toolbox
before pushing (74s locally), and the PR gate re-runs it authoritatively.

push: [main] is KEPT -- post-merge main must still be verified, and it is the only run for
which no PR context exists.

FOLLOW-UP once this and #5 are both merged: the feat/ rationale in
infra/plex/claim-ship.sh becomes obsolete and its comment should be trimmed. The script
keeps working either way.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

.gitea/workflows/gate.yml

@@ -44,16 +44,31 @@
 ---
 name: gate
 
+# TRIGGERS — deliberately only `pull_request` into main, plus `push` to main itself.
+#
+# There is NO per-branch push trigger. There used to be a prefix list (feature/** fix/**
+# docs/** chore/**) for "fast feedback on the branch", and it was a net negative here:
+#
+#   * `act_runner` runs at capacity 1. A branch push and its PR fire the SAME gate over the
+#     SAME tree, and the redundant run SERIALISES AHEAD of the PR run — doubling the wall
+#     clock on the one result that actually gates the merge. That cost real time during the
+#     2026-09-29 plex claim, where the loop is racing a short-lived token.
+#   * The list silently did not match this repo's own convention. Branches here are `feat/**`,
+#     which was absent, so the "fast feedback" never fired for the most common prefix anyway —
+#     a mismatch nobody noticed for a month because its only symptom was a MISSING run.
+#     Any hand-maintained prefix list has that failure mode; deleting it removes the class.
+#   * It is redundant. CLAUDE.md already requires `./ci/gate.sh` in the pinned toolbox before
+#     you push (74s locally), and the PR gate re-runs it authoritatively. A third run of the
+#     same checks buys nothing.
+#
+# `push: [main]` is KEPT: post-merge main must still be verified, and it is the only run for
+# which no PR context exists.
 on:
   pull_request:
     branches: [main]
   push:
     branches:
       - main
-      - 'feature/**'
-      - 'fix/**'
-      - 'docs/**'
-      - 'chore/**'
 
 concurrency:
   group: gate-${{ github.ref }}