feat(ci): scheduled weekly lock bump + dispatch fast-lane (item 14 b+c)

.gitea/workflows/bump.yml: Mondays 05:17 UTC (+ workflow_dispatch for
security bumps), nix flake update — within the pinned release branches
by construction, never a release jump — gated by nix flake check
--no-build, then a pathspec-limited flake.lock commit pushed to main
with the update's change list as the body. That push triggers check.yml
as a second net. Red gate or push race = a visibly failed run, nothing
lands. v1 promotion stays human. py_compile/bash -n deliberately not in
the gate: they don't read the lock. Container recipe inherited from
check.yml (nixbld, sandbox=false, pinned Nix 2.31.5).

Verified: V0 (yq parse, bash -n per run block); the update/commit/push
logic simulated end-to-end in a scratch clone with a real nix flake
update and a bare remote (changed + unchanged branches, bystander file
stays uncommitted, push lands); today's bumped lock evals green.
Remains: the first real run (cron pickup + Actions-token push) is not
confirmable from a session — BACKLOG item 14 slimmed to that watch.

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

agent/MEMORY.md

@@ -13,6 +13,9 @@ iteration would otherwise rediscover.
   `sandbox=false` for Stylix IFD, Nix pinned 2.31.5 vs lazy-trees, no JS
   actions past node20) — learned over the legacy repo's 57 runs; read
   them before touching the workflow.
+- The Gitea instance is **1.25.4** — `on: schedule` workflows are
+  supported; bump.yml assumes the Actions token can push to `main`
+  (standard Gitea behaviour, but unconfirmed until the first run lands).
 - The git server is **Gitea** (gitea/act_runner via docker-compose), NOT
   Forgejo — workflows are read from `.gitea/workflows/` (or `.github/`),
   never `.forgejo/workflows/` (a whole push cycle was lost to that).