fix(agent-hooks): drain stdin before hook script early exits so agents never hit EPIPE (#8430)

* Fix hook scripts to drain stdin before any early-exit path

Generated agent hook scripts and missing-script launchers could exit
successfully before consuming the payload written to their stdin,
leaving the writer with a broken pipe (EPIPE/ERROR_BROKEN_PIPE) once
the reader closed early. Capture stdin (or drain it via a shared
epilogue/fast-path guard) before any whole-script success exit across
all POSIX, batch, PowerShell, and Git Bash launcher variants, and add
a cross-agent lifecycle test suite plus a live Electron verification
script to guard the contract going forward.

* Harden hook scripts against unreadable managed scripts and add a Claude/

- Extend the POSIX launcher guard to also require `[ -r ]`, not just `-f`/`-x`,
  so an executable-but-unreadable managed script still drains stdin instead of
  erroring or silently misbehaving.
- Add a verifier case (`verifyClaudeDevinSkip`) that spins up a local HTTP
  server and confirms the Claude hook never forwards a request that Devin
  already imported, catching accidental double-forwarding.
- Update installer-utils tests and stdin-lifecycle docs to match the new
  readable-file guard and the added verification case.

* Fix hook-launcher verification to derive script paths from the installed

Extract the quoted path from the launcher's `if [ -f '...'` clause instead of
reconstructing it via join(home, ...), so missing/failing-script test cases
can't silently fall through to the real script if the install layout changes.

---------

Co-authored-by: Jinjing <6427696+AmethystLiang@users.noreply.github.com>

src/main/command-code/hook-service.test.ts

@@ -58,7 +58,7 @@ describe('CommandCodeHookService', () => {
       expect(config.hooks.PreToolUse[0].hooks[0].command).toContain(join(homeDir, '.orca'))
     }
     if (process.platform !== 'win32') {
-      expect(config.hooks.PreToolUse[0].hooks[0].command).toMatch(/^if \[ -x /)
+      expect(config.hooks.PreToolUse[0].hooks[0].command).toMatch(/^if \[ -f /)
     }
   })