(test): cover terminals, restore, triggers and the sidebar with e2e journeys

[devsuitup]

e2e is now a required check (#304, #432), but its five journeys cover only the file panel and the Changes tab. A regression elsewhere is seen only by jsdom tests, which have no layout and no real IPC.

Add four coarse journeys on the critical paths, with the same rules as docs/e2e.md (isolated HOME/data/triggers dir, plain terminals and fixture repos, never a real claude, structure and geometry assertions, no waitForTimeout):

1. A plain terminal starts, prints output that reaches the xterm screen, accepts input, and closes (pty spawn, renderer flush, exit handling).
2. Session restore: open two plain terminals, relaunch the app on the same data dir, both come back in the sidebar and the grid.
3. Trigger watcher end to end: a trigger file in the isolated triggers dir types a command into a plain terminal; its output appears and the result file reports it sent.
4. Sidebar and grid render fixture sessions (synthetic JSONL transcripts under the isolated ~/.claude/projects): projects grouped, counts right, grid toggle switches layout.

Also write the rule into docs/e2e.md: a bug that only shows in the running app gets a journey in its fix PR, and that journey is its red-first test.

Acceptance: each journey goes red under a mutation of the path it covers (listed in the PR); the job stays under one minute on ubuntu; ten consecutive green runs before merge.

[devsuitup]

Add to this card (found while live-testing v0.0.88, 03/10): e2e/fixtures.js isolatedEnv does not drop ORIGINAL_PATH. Under a Git Bash parent, Git's /etc/profile rebuilds PATH from it, so a journey that clicks a session row would start the REAL claude (it happened once in a scratch run, under the temp HOME, no harm). Drop ORIGINAL_PATH, put a fake claude first in the temp HOME's PATH, and assert type -a claude resolves to the fake before any journey that opens a session.