Re-sign electrobun's CLI binary so the app actually launches

`bun run start` printed nothing and exited 0 without ever opening a window.
electrobun's prebuilt CLI is a Bun single-file executable whose payload is
appended after the linker ad-hoc signed it, so `codesign -v` reports "code or
signature have been modified" and the macOS kernel SIGKILLs it at exec. The
failure was invisible because bin/electrobun.cjs spawns the real binary and
forwards `process.exit(code || 0)` — a signal death has `code === null`.

Confirmed upstream, not local corruption: a fresh download from the GitHub
release hashes identical to the shipped copy and fails the same check. Both
the darwin-arm64 and darwin-x64 CLI tarballs are affected.

scripts/fix-electrobun-cli.ts re-seals the binary with `codesign --force
--sign -`. It runs from postinstall AND ahead of every electrobun invocation,
because the wrapper downloads the CLI lazily on first use rather than at
install time — postinstall alone would no-op on a fresh checkout. When the
binary is missing it provokes that download first, so a clean tree self-heals.
It also fixes .cache/electrobun, which the wrapper restores bin/ from, and
release.ts re-signs the Rosetta x64 CLI on download and on cache reuse.

Idempotent (~0.3s when already valid) and a no-op off macOS. Verified from a
deleted-binary state: `bun run start` downloads, re-signs and launches.

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

docs/gotchas.md

@@ -31,6 +31,21 @@ touching the adjacent code.
 
 ## Electrobun
 
+- **The prebuilt CLI binary ships with a broken ad-hoc signature**, so macOS
+  SIGKILLs it at exec and `bun run start` prints nothing and exits **0** —
+  `bin/electrobun.cjs` spawns the real binary and forwards
+  `process.exit(code || 0)`, and a signal death has `code === null`. The binary
+  is a Bun single-file executable whose payload is appended *after* the linker
+  signed it, so `codesign -v` reports "code or signature have been modified";
+  the arm64 and x64 CLI tarballs are both affected upstream (confirmed by
+  hashing a fresh download against the shipped copy — it is not local
+  corruption, and re-installing does not help). `scripts/fix-electrobun-cli.ts`
+  re-seals it with `codesign --force --sign -`. It runs from `postinstall`
+  **and** ahead of every electrobun invocation, because the wrapper downloads
+  the binary **lazily on first use**, not at install time — postinstall alone
+  would no-op on a fresh checkout. It also fixes `.cache/electrobun`, which the
+  wrapper restores `bin/` from. Never read a silent `exit 0` from the
+  electrobun CLI as "nothing happened": run `codesign -v` on it first.
 - **Window `close` is not cancellable** (response type `{}`; only the
   app-level `before-quit` supports `event.response = {allow:false}`). All
   unsaved-state guards must either intercept app-controlled close paths