Improve workspace, agent orchestration, and dock UX

[duolahypercho]

What changed

• Add the project-first hub, transcript helpers, graph workspace handling, and the latest agent/session orchestration updates.
• Improve agent activity, checkpoints, reasoning, side chat, loop/report flows, and related RPC/core behavior.
• Make the right-side workspace dock start blank on first use, offer a tab chooser, open missing tabs when agent actions target them, and return to the blank chooser when the final tab is closed.
• Update unit, end-to-end, and workspace coverage for the new behavior.

Why

This consolidates the current CaliCode worktree into one coherent workspace and agent experience. The dock no longer guesses which tool belongs on screen, while project and agent state remain recoverable across navigation and reloads.

Validation

• cargo fmt --check
• cargo clippy --all-targets -- -D warnings
• cargo test (1060 passed, 17 ignored)
• client: pnpm test -- --run (902 passed)
• client: pnpm exec tsc -b --noEmit
• client: pnpm build

The full Playwright E2E suite was not run because the packaged CaliCode app was already holding core port 8765 during verification.