docs: fix stale platform/ paths left over from monorepo extraction

[ayobamiseun]

What

Fixes stale platform/ path references left over from the monorepo extraction, across 9 files. Comment/doc changes only — no behavior change.

1. surfaces/gui/README.md — every command referenced a platform/ directory that doesn't exist in this repo, so a fresh checkout could not follow the GUI README at all.
2. 7 Python files — docstring/comment citations of platform/docs/FAKE-SLACK-SPEC.md and platform/docs/PERSONAS.md normalized to docs/... (tests/conftest.py, tests/test_fake_slack.py, coworker/connectors/adapters.py, coworker/connectors/senders.py, coworker/personas/__init__.py, coworker/testing/fake_slack/server.py, coworker/testing/fake_slack/__init__.py).
3. surfaces/gui/src-tauri/src/lib.rs:57 — the doc comment on server_bin() said the dev fallback is platform/.venv, but the code below resolves ../../../.venv from src-tauri, i.e. the repo-root .venv. Comment now matches the code.

Before / after

Before (surfaces/gui/README.md) — none of these paths exist:

bash platform/packaging/setup_dev_env.sh   # → platform/.venv (...)
cd platform
./.venv/bin/openworker-server --cwd /path/to/your/project --port 8765
cd platform/surfaces/gui

After — matches the top-level README and the actual repo layout (verified: packaging/setup_dev_env.sh:11 creates the venv at repo-root .venv):

bash packaging/setup_dev_env.sh   # → .venv (...)
./.venv/bin/openworker-server --cwd /path/to/your/project --port 8765   # from repo root
cd surfaces/gui

Verification

• All edited Python files pass python -m py_compile.
• grep -rn "platform/" over *.py/*.md now returns zero stale path references.
• No UI or runtime code touched, so no screenshots — the before/after above is the user-visible change.

Note: docs/FAKE-SLACK-SPEC.md and docs/PERSONAS.md still don't exist in this repo even at the corrected path — the citations now at least point at the right location; restoring those docs seems worth its own issue/PR.

🤖 Generated with Claude Code