Fix real workflow bugs a review found: dead bind mount, blind error gate

A review found the "Validate with makepkg and namcap" step's bind mount
(docker run -v "$PWD/rendered:/work") would very likely fail on Gitea's
own act_runner: a containerized job's $PWD isn't a path the daemon's host
can resolve, so the mount would silently attach an empty directory
instead of failing loudly — the same class of problem noted elsewhere for
this exact environment. Switched to docker create + docker cp (in and
back out) + docker start -a, the pattern already validated locally, which
works regardless of where the daemon actually lives.

Also found and fixed, most severe first:

- The namcap error gate (`grep -q "^[a-zA-Z0-9_-]*bin E:"`) only matched
  one of namcap's two line shapes for reporting an error
  ("triple-c-bin E: ...") and missed the other ("PKGBUILD
  (triple-c-bin) E: ...") entirely — confirmed by reproducing both against
  a real namcap run. The PKGBUILD-level half of the safety net was dead.
  Replaced with a plain `grep -q " E: "`, confirmed to match both real
  shapes (and a split-package variant) and nothing else.
- package()'s `ar x "Triple-C_${pkgver}_amd64.deb"` named the asset
  literally, defeating the whole point of the resolve step discovering
  the real filename from the release instead of assuming a pattern — a
  future Tauri bundler naming change would still break here with an
  opaque error. Changed to `ar x ./*_amd64.deb`, which `source=()` already
  guarantees matches exactly one file.
- `pacman -Sy` before installing packages is the canonical Arch partial-
  upgrade footgun; changed to `pacman -Syu --noconfirm --needed`.
- `${{ inputs.version }}` was interpolated directly into a shell step
  instead of routed through `env:`, unlike every other step in the file.
- `git push origin master` assumes the local branch name after cloning a
  brand-new (not-yet-created) AUR repo's empty state is `master`, which
  depends on the runner's own `init.defaultBranch` if the server sends no
  symref. `git push origin HEAD:master` is unambiguous either way.
- The private key was written with a plain redirect then chmod'd after,
  leaving a window where it's world-readable; now created at its final
  mode first via `install -m 600 /dev/null`. Added `-o IdentitiesOnly=yes`
  so a runner ssh-agent can't offer a different key first.
- Added GH_PAT auth to the api.github.com calls, matching every other
  workflow in this repo, to avoid the unauthenticated 60/hour rate limit.
- Fixed two comments: the `options` comment credited `!debug` for
  suppressing the empty debug-package directory, when it's actually
  `!strip` doing that (verified in a real build); and documented in the
  README that a hand-edit made directly in the AUR repo is silently
  reverted by the next dispatch, since every run renders fresh from this
  repo's template.

All of the above re-verified with the same real end-to-end methodology as
the original commit: real makepkg build, real namcap lint (clean), and
the exact updated docker create/cp/start sequence run against a live
container.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FGjXq6fqtAFHdbhk4f3PfZ

packaging/arch/README.md

@@ -44,3 +44,10 @@ the workflow rewrites them for every real publish and never commits the
 result back here, so don't read this file's `pkgver` as "the last published
 version." Everything else (`depends`, `pkgdesc`, `package()`) is meant to be
 edited by hand normally, the same as any other PKGBUILD.
+
+**A hand-edit made directly in the AUR repo is silently overwritten the
+next time this workflow runs.** Every run renders fresh from *this*
+repo's template rather than starting from whatever AUR's copy currently
+looks like, so a quick fix pushed straight to AUR (bumping `pkgrel` for a
+packaging-only issue, say) survives only until the next dispatch. Make
+the fix here instead.