refactor: reshape tree, break up god-files, go all-absolute imports

[Juliusolsson05]

Reshapes the app tree into per-process + per-feature subtrees, breaks the four inhabited god-files, and moves every cross-domain import onto the five domain aliases. 26 commits, behavior-preserving.

The biggest files are gone:

file	before	after
workspaceStore.ts	5475	52
Feed.tsx	2817	904
TileLeaf.tsx	1249	335
main/index.ts	1144	135

Feed splits into ui/markdown/, ui/semantic/, ui/rows/ (plus a scaffolded context.tsx, types.ts, scroll.ts, lib/). TileLeaf splits into a TileLeaf/ sibling directory with the paste-state-machine helpers, the image-handling helpers, labels, five presentational subcomponents (PaneHeader / QueueStrip / CompactionStrip / PaneToast / ScrollIndicator), four hooks (useComposerAutoGrow / useTypeToFocus / usePromptHistory / useClaudeImagePaste), and the composer itself (ComposerInput + useComposerKeybinds — the 310-line onKeyDown). workspaceStore decomposes into 25 focused sub-hooks under workspace/hook/; the root file is now a 52-line re-export shell so external callers keep their existing import paths.

The repo root is now {src, packages, vendor} instead of ten loose peers. packages/ holds the three in-house submodules (agent-transcript-parser, claude-code-headless, codex-headless); vendor/ holds the upstream read-only slabs (codex-src submodule + gitignored claude-code-src).

All cross-domain imports go through five aliases — @main, @preload, @renderer, @shared, @providers — matched in both tsconfigs and electron.vite.config.ts. Zero relative imports remain in src/. One exception is the path.join call in mainWindow.ts that locates the preload bundle on disk (not an import) — the first alias sweep mistakenly rewrote it as a path alias, which shipped a black-screen boot regression before being reverted with a guard comment so the next sweep can't hit the same trap.

The branch also fixes three things that surfaced during the refactor. The workspaceStore decomposition silently broke the bootstrap-replay debounce timer because the new refs factory returned a fresh object literal each render; the IPC sub-hook's dep-array cleanup then tore down and re-attached subscriptions on every tick, and clearTimeout killed the timer that flipped bootstrapping back to false — pinning Feed's auto-scroll and lazy-mount behind a stuck flag. Memoizing the refs wrapper with an empty dep array restores stable identity. The providers config bridge — a combined ProviderConfig = RendererProviderConfig & MainProviderConfig type and the per-provider config.ts files that implemented it — forced Claude's Node-only session code to sit next to React components, dragging the renderer subtree into the node tsc project; deleting the bridge plus adding explicit tsconfig excludes for renderer halves of the providers took node tsc errors from 731 to 145. And the Phase-5 monorepo move broke the claude-code-headless proxy runtime: the mitmdump lookup candidate list still referenced the old claude-code-headless/ path, the Python venv shebangs inside .proxy-testing/venv/bin/ hardcode their absolute install location (so they ENOENT after a directory move), and mitmdump failing to start surfaced as a 10-second silent CA-wait timeout. The submodule now checks packages/claude-code-headless/.proxy-testing/… first, shares a single mitmproxy CA confdir across sessions, and throws a real error with mitmdump's stderr tail when the child exits before the CA lands.

What's not in scope: the three rendering-duplication bugs (optimistic ghost + committed user turn, Codex <environment_context> rendering as a user bubble, semantic-turn painting after the rollout commits the same content) — those exist on main too; this branch is deliberately behavior-preserving. Same for the carry-over findings from the earlier code review (ghost restart keyed to transient sessionId, Codex older-history pagination loop, empty-feed WorkIndicator gap, feed-debug write-order, semantic-collapse hiding live output). The optional fat-files sweep (sessionIndex 727, GitRows 610, sessionManager 579, AgentActivityModal 502, PromptSearchModal 442) is also deferred; those are large but coherent, not god-files.