AppForge-1 — install an app from a local folder or .brainstorm file (sideload path + packaged-path fix)

[th3-br41n]

AppForge-1 — install an app from a local folder or .brainstorm file

First real producer of the already-schema'd sideload path (InstallOrigin.LocalFile): a user can now install an app bundle they have on disk, straight from the Marketplace. This is the install half of the "app built inside Brainstorm becomes a real app" loop.

What's new

• apps:install-from-folder / apps:install-from-file IPC (main/ipc/sideload-handlers.ts): main-side OS dialog (openDirectory, and openFile filtered to *.brainstorm per the dialog-filter rule) → manifest pre-check → AppInstaller.install with InstallOrigin.LocalFile provenance → dashboard icon pinned (mirrors the catalog install path). Results are always a typed SideloadInstallResult (installed with app summary + granted caps | cancelled | failed with a SideloadFailureCode) — the handler never throws raw errors at the renderer.
• Marketplace UI: an "Install from…" toolbar button opening a shared fancy-menus picker (folder / .brainstorm), success/failure toasts (typed-code → message map), and honest unsigned surfacing — a "Local install" source label, an Unsigned advisory chip + Signature spec row on the listing detail (signatureStatus now flows registry row → MarketplaceService → listing wire type).
• Packaged-path fix: registerMarketplaceHandlers resolved first-party bundles via a __dirname relative walk that lands inside the asar in packaged builds — now resolveFirstPartyAppsDir picks process.resourcesPath/apps when app.isPackaged (same tree bootstrapApps uses). reinstallFirstPartyApp gains prebuiltOnly (passed as app.isPackaged): installs the prebuilt extraResources bundle with bootstrap-cache provenance and never spawns vite build in a packaged shell.

Security posture (⚠️ flagging for security review — new IPC + install surface)

This is hostile-input handling; the following is the intended posture, please poke at it:

• Privileged surface: the two channels are exposed only on the dashboard preload, and additionally sender-checked in main against the dashboard WebContents — any other sender gets a typed not-allowed failure (fail-closed). App renderers cannot reach the installer.
• User gesture: the bundle path only ever comes from an OS dialog the user drove; the renderer cannot pass a path.
• Untrusted manifest: size-bounded read (512 KiB) before parse; the installer's fail-closed validator is authoritative (the handler pre-runs it only to classify typed failures). Tested from this call site: traversal in entry, malformed id, non-JSON, oversized.
• Untrusted archive: file size-bounded before read (64 MiB default); decompression expansion-bounded via new unpackBundle({ maxOutputBytes }) (gzip-bomb defense, 256 MiB default); unpack goes to a fresh mkdtemp staging dir removed in finally; the tar codec's absolute/.. rejection + unpackBrainstormBundleToDir's per-entry containment re-check are both exercised from this call site (zip-slip test).
• Signature policy unchanged: unsigned installs record AppSignatureStatus.Unsigned (advisory in v1, shouldBlockInstall remains the single enforcement chokepoint); trust quarantine (sideloaded action tier) applies as before. The unsigned state is surfaced to the user rather than hidden.

Tests

• main/ipc/sideload-handlers.test.ts (new, 13 cases): happy folder install (registry row provenance + icon pin + unsigned surfaced), cancel, hostile manifests (traversal entry / bad id / bad JSON / oversized), id collision, non-dashboard sender, no-session, .brainstorm round-trip via packBrainstormBundle, garbage bytes, zip-slip entry, over-limit file, decompression bomb.
• main/dev/seed-demo-apps.test.ts: prebuiltOnly installs with bootstrap-cache provenance and a spawn spy proves vite build is never spawned (including the missing-bundle failure path).
• main/apps/first-party.test.ts: resolveFirstPartyAppsDir dev + packaged branches.
• main/catalog/brainstorm-package.test.ts: maxOutputBytes bomb bound (tiny archive, big expansion → throws; within bound → unpacks).
• bun run verify, bun run lint, bun run typecheck green.

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