feat: agent-browser config in project state #351

Why

agent-browser config and Chrome live at user level today (design: What this replaces).

In scope

Config in project state; a system Chrome first, otherwise Chrome in the cache.

Out of scope

Other browsers.

Acceptance criteria

• ~/.agent-browser and ~/.config/agentic-kit are untouched

Dependencies

Blocked by: #339

Blocks: #386

Plan

• Release: 4.0.0-beta.2
• Size: size:M · Workstream: ws:project-scope
• Epic: feat: project-scope P4, Brain, agent-browser, embeddings and Superpowers (epic) #299
• Card: P4-02 in the card inventory
• Sources: Design (docs(plans): project-scoped management design and its prerequisites #289) What this replaces; Supersession ledger (docs(plans): v4 GA master plan, supersession ledger and v5 registers #290) ADR-0043

Verification

• Contract test from test: contract tests with the current violations as baseline #328