refactor(extension): extract target-neutral recorder host and platform layer

[ManthanNimodiya]

Groundwork for a Firefox port, zero Chrome behavior change.

Renames offscreen.html→recorder.html and src/offscreen/→src/recorder/; extracts the offscreen lifecycle into src/background/recorder-host.ts; adds src/platform/ (compile-time TARGET, capability flags, EXTENSION_PROTOCOL).

Fixes three sender checks that hardcoded chrome-extension: (on Firefox they'd misclassify extension pages as web pages).

Pins the recorder to the streaming pipeline explicitly (selectRecordingPipelineFromSupport(..., { preferStreamingUpload: true })) since the UA heuristic in recorder-core returns false on Firefox; Chrome output unchanged.

Greptile Summary

This PR splits the extension recorder into target-neutral pieces. The main changes are:

• Renamed the offscreen recorder entrypoint to recorder.html.
• Moved recorder code under src/recorder.
• Extracted Chrome offscreen lifecycle handling into recorder-host.ts.
• Added platform target, capability, and extension protocol helpers.
• Updated sender checks and recorder pipeline selection.

Confidence Score: 4/5

The Firefox-target path can still load Chrome-only recorder-host code and can default to Chrome capabilities.

• The renamed Chrome recorder entrypoint is wired consistently.
• The service worker imports recorder-host.ts before any offscreen capability guard can run.
• The target helper falls back to Chrome when the build does not inject __TARGET__.

apps/chrome-extension/src/background/recorder-host.ts, apps/chrome-extension/src/platform/target.ts, apps/chrome-extension/vite.config.ts

Important Files Changed

Filename	Overview
apps/chrome-extension/recorder.html	Renames the recorder HTML entrypoint and points its module script at the new recorder path.
apps/chrome-extension/src/background/recorder-host.ts	Extracts offscreen document lifecycle handling, but imports Chrome-only runtime APIs without a Firefox-safe guard.
apps/chrome-extension/src/background/service-worker.ts	Uses the new recorder host and protocol helper while preserving the existing sender-token checks.
apps/chrome-extension/src/platform/capabilities.ts	Adds target-specific capability flags for Chrome and Firefox.
apps/chrome-extension/src/platform/extension-protocol.ts	Derives the extension protocol from the runtime instead of hardcoding Chrome's protocol.
apps/chrome-extension/src/platform/target.ts	Adds the compile-time target helper, but an absent target define currently falls back to Chrome.
apps/chrome-extension/src/recorder/recorder.ts	Moves the recorder module, adds a best-effort AudioContext resume, and pins pipeline selection to streaming upload.
apps/chrome-extension/vite.config.ts	Updates the Rollup input from the old offscreen HTML file to the new recorder HTML file.

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
apps/chrome-extension/src/background/recorder-host.ts:14
**Firefox Worker Imports Chrome APIs**

`recorder-host.ts` is imported by the service worker at module load time, but this line reads `chrome.runtime.ContextType.OFFSCREEN_DOCUMENT` before any capability guard can run. In a Firefox build where that Chrome-only API is missing, the background worker can throw during startup instead of reaching the `supportsOffscreen` checks.

### Issue 2 of 2
apps/chrome-extension/src/platform/target.ts:8
**Missing Target Becomes Chrome**

`TARGET` defaults to `"chrome"` whenever `__TARGET__` is absent, but the changed Vite config does not define `__TARGET__`. A Firefox build that uses this config without an injected define will enable Chrome-only capabilities like offscreen and tab capture, sending the Firefox worker into unsupported APIs.

_{Reviews (1): Last reviewed commit: "refactor(extension): extract target-neut..." | Re-trigger Greptile}

Greptile also left 2 inline comments on this PR.

Context used:

• Context used - CLAUDE.md (source)
• Context used - AGENTS.md (source)

[tembo]

chrome.runtime.getContexts can invoke the callback with contexts undefined (or fail in older runtimes), which would make hasRecorderHost() throw on .length. Small hardening tweak:

Suggested change

	(contexts) => resolve(contexts),
	(contexts) => resolve(contexts ?? []),

[greptile-apps]

Firefox Worker Imports Chrome APIs

recorder-host.ts is imported by the service worker at module load time, but this line reads chrome.runtime.ContextType.OFFSCREEN_DOCUMENT before any capability guard can run. In a Firefox build where that Chrome-only API is missing, the background worker can throw during startup instead of reaching the supportsOffscreen checks.

Prompt To Fix With AI

This is a comment left during a code review.
Path: apps/chrome-extension/src/background/recorder-host.ts
Line: 14

Comment:
**Firefox Worker Imports Chrome APIs**

`recorder-host.ts` is imported by the service worker at module load time, but this line reads `chrome.runtime.ContextType.OFFSCREEN_DOCUMENT` before any capability guard can run. In a Firefox build where that Chrome-only API is missing, the background worker can throw during startup instead of reaching the `supportsOffscreen` checks.

How can I resolve this? If you propose a fix, please make it concise.

[greptile-apps]

Missing Target Becomes Chrome

TARGET defaults to "chrome" whenever __TARGET__ is absent, but the changed Vite config does not define __TARGET__. A Firefox build that uses this config without an injected define will enable Chrome-only capabilities like offscreen and tab capture, sending the Firefox worker into unsupported APIs.

Prompt To Fix With AI

This is a comment left during a code review.
Path: apps/chrome-extension/src/platform/target.ts
Line: 8

Comment:
**Missing Target Becomes Chrome**

`TARGET` defaults to `"chrome"` whenever `__TARGET__` is absent, but the changed Vite config does not define `__TARGET__`. A Firefox build that uses this config without an injected define will enable Chrome-only capabilities like offscreen and tab capture, sending the Firefox worker into unsupported APIs.

How can I resolve this? If you propose a fix, please make it concise.