P10 Days 1-5 - Phantom - Browser Agent

[theschoolofai]

Sub-issue for parent #12.\n\n## Phase\n- Days 1-5 (2026-02-17 to 2026-02-21)\n\n## Scope\n- Build browser session abstraction and deterministic action primitives.\n\n## Exit Criteria\n- [ ] Scope implementation merged via PR\n- [ ] Relevant tests for this phase pass in CI\n- [ ] Delivery README updated with evidence

[theschoolofai]

Leaving this issue open. After the final capstone integration pass, this track still has genuinely unresolved work that did not fully land in current master, so it should remain open until that scope is either completed or explicitly retired.