Add T3 Code nightly package (#793)

* Add T3 Code nightly package

* Hold a T3 Code nightly until its AppImages have uploaded

Upstream's release workflow publishes the GitHub release before softprops/action-gh-release uploads its assets: across the last 70 nightlies the AppImages finished 13 to 133 seconds after publication. A scheduled sync that lands in that window selects the release, finds no ARM AppImage to hash, and fails the shared sync run. A 30-minute minimum age, the hold omarchy-dev already uses, makes the watcher keep the previous nightly until the new one is complete.

Co-Authored-By: Codex XHigh <noreply@openai.com>

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Co-authored-by: Codex XHigh <noreply@openai.com>

pkgbuilds/t3code-nightly-bin/README.md

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+# T3 Code Nightly
+
+`t3code-nightly-bin` packages upstream nightly releases for x86_64 and aarch64.
+Run `t3code-nightly` for the desktop or `t3-nightly` for the server CLI.
+The app launcher entry is **T3 Code (Nightly)**. Optional Electron flags go in
+`~/.config/t3code-nightly-flags.conf` (or under `$XDG_CONFIG_HOME`).
+
+The package can be installed alongside `t3code-bin`, with separate binaries,
+icons, and desktop entries. Upstream still shares its application data and URL
+schemes between channels: installing both does not create isolated profiles.
+
+The upstream watch accepts only `vX.Y.Z-nightly.YYYYMMDD.N` releases. Arch versions
+replace the hyphen with an underscore; downloads retain upstream's original tag
+and filenames. Both architecture checksums must be available before an update.
+A nightly is picked up once it is 30 minutes old, because upstream publishes the release before its AppImages finish uploading.