fix: OS-aware startup workflow and cross-browser audio recording

[mlarsen-source]

Summary

The run-project.md agent workflow was restructured from a loosely ordered single-platform guide into an 8-step OS-aware sequence: OS and terminal detection now runs first, followed by per-platform prerequisite checks for Python, Node.js, pnpm, ffmpeg, and Homebrew (macOS only), before any project-level setup is attempted. The MediaRecorder initialization in InterviewClient.tsx was fixed to use MediaRecorder.isTypeSupported() with a fallback chain instead of hardcoding audio/webm, which caused Groq Whisper to receive a mismatched or undecodable audio file on Safari and Firefox, resulting in hallucinated "Thank you" transcription output.

Issues fixed

Fix	Root cause	Affected users
OS-aware startup workflow (modified)	Single command set failed across Windows PowerShell, macOS, and Linux; ffmpeg and Homebrew not checked	Any user not on Windows Git Bash
Cross-browser audio recording (modified)	Hardcoded audio/webm unsupported on Safari; mislabeled blob caused Whisper format mismatch	Safari users; any browser that doesn't support webm

File-by-file changes

Documentation

• docs/agent-workflows/run-project.md: Rewrote the workflow as an 8-step OS-aware sequence — Step 1 detects the OS via uname -s and asks the user if the result is unrecognized; Steps 2–3 check and fix OS-level prerequisites (Python, Node.js, pnpm, ffmpeg, Homebrew on macOS) before touching the venv; Steps 4–5 handle project-level state; Steps 6–8 start backend and frontend and report URLs; every step now provides platform-specific commands for Windows PowerShell, Windows Git Bash, macOS, and Linux separately.

Frontend

• frontend/app/InterviewClient.tsx: Replaced the hardcoded { mimeType: "audio/webm" } MediaRecorder option with a isTypeSupported() fallback chain that selects audio/webm;codecs=opus, audio/webm, audio/mp4, or the browser default in that order; the detected mimeType is passed to both the MediaRecorder constructor and the final Blob so the uploaded filename extension matches the actual container format Groq Whisper receives.