perf(electron): look up the login shell PATH without blocking the main thread (#1784)

* perf(electron): look up the login shell PATH without blocking the main thread

fix-path ran $SHELL -ilc env synchronously right after the first load.
With a typical zsh profile that held the main thread for 1-2 s, while the
database worker's ready message and the renderer's first IPC calls waited,
so the launch journey's first card came that much later. Use shell-path's
async shellPath() with fix-path's fallback, so the resulting PATH is the
same and the main thread stays free.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* docs(perf): name the PR that made the login shell PATH lookup async

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(electron): let bare-name player spawns wait for the login shell PATH

With the lookup now asynchronous, an external player launched (or the
Linux embedded MPV support check, which runs and caches a bare
`mpv --version`) within the first seconds could see the inherited PATH.
The OPEN_MPV_PLAYER / OPEN_VLC_PLAYER handlers and every embedded MPV
handler now await waitForLoginShellPath() (settled lookup, at most 10 s,
immediate on Windows), restoring the guarantee the blocking lookup gave.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(electron): wait for the login shell PATH only for bare-name spawns

External players wait only when they resolve to a bare name (no
configured path, no well-known install found); a path to an executable
starts at once. Embedded MPV waits only on Linux and only for support and
prepare, which run the cached bare-name `mpv --version` check; sessions
and controls never wait.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(electron): wait for the login shell PATH only before the mpv probe

Embedded MPV support and prepare waited on every Linux call, although
getSupport() returns before the bare-name `mpv --version` probe for the
frame-copy engine, native Wayland, a disabled feature or a cached result.
willProbeLinuxMpvExecutable() now gates the wait on the probe actually
running.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(electron): stop waiting for a login shell that already timed out once

After the first wait for a hung `$SHELL -ilc env` runs out, later
bare-name player launches and Linux mpv probes proceed at once instead
of each waiting the full limit again.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(electron): bound login shell PATH waits by the lookup's own budget

Replace the latch on the first expired wait with a deadline set when the
lookup starts (10 s). Every wait ends when the lookup settles or the
deadline passes: a launch retried while the shell is still within its
budget waits for the PATH again, and once the budget is spent no launch
waits, so a hung shell still delays at most the first seconds.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(electron): re-probe a missing mpv once a late login shell answers

When the PATH lookup runs out of budget, the Linux embedded MPV support
check probes `mpv --version` with the inherited PATH and caches a
missing result for the rest of the session. waitForLoginShellPath() now
reports whether the lookup settled; after a timed-out wait the handler
forgets a cached "missing" once the lookup finishes, so the next support
check probes again with the login shell PATH.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(electron): share one deadline among waits before the PATH lookup starts

A bare-name launch that waited before the lookup was scheduled started
its own 10 s limit, so while startup was stuck every retry paid the full
delay again. The first early wait now sets the shared deadline; the
lookup still replaces it with its own budget when it starts.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(electron): re-probe mpv after a late login shell PATH either way

A Linux mpv probe that ran on the inherited PATH can be wrong in both
directions: the login shell PATH may add mpv or drop the directory the
inherited one found it in. forgetLinuxMpvExecutableProbe() now clears a
found result as well as a missing one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(electron): skip the login shell PATH wait for Flatpak host launches

In Flatpak, players start through `flatpak-spawn --host`, which resolves
the name with the host's PATH; the sandbox's login shell lookup cannot
change it. The launch handlers now decide from the same launch context
the player uses: no wait in flatpak-host mode, otherwise only for a bare
player name.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: 4gray <fourgray@proton.me>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

docs/architecture/performance-journeys.md

@@ -421,6 +421,17 @@ process before the first card.
   completion bumps `EpgSourceSettingsService.revision()`, the fence that
   keeps XMLTV lookups from returning data of a removed source.
 
+- The main thread must stay free between the load and the first card. The
+  renderer's first database read creates the database worker, and every
+  request waits until the main process has handled the worker's `ready`
+  message. Until #1784 the login-shell PATH lookup (`fix-path`) ran right
+  after `bootstrap-events:done` and spawned `$SHELL -ilc env` synchronously:
+  on a Mac with a typical zsh profile it held the main thread for about
+  1-2 s, the first `dbGetAppState` resolved about 2.3 s after spawn, and
+  everything after it (about 20 ms of IPC) waited. It now runs the shell
+  asynchronously (`startup/login-shell-path.ts`). On Linux runners bash
+  starts in tens of milliseconds, so the effect there is small.
+
 Validation (#1716, Principle 3): deferring the download list, update status
 and dashboard recent/favorites reads until after the first render took the
 counter from 12 to 7 on a Mac, but moved neither `spawnToFirstCardMs` nor