Simplify PR context model: remove Disconnect action and drop disconnected state

[knightedcodemonkey]

Problem

Our current PR context model includes disconnected plus a dedicated Disconnect button. This creates extra transition paths and persistence branches that increase complexity and contribute to state/race bugs during workspace switching.

At the same time, we now have a stricter Workspaces UX:

1. Select repository scope
2. Select stored/starter context
3. Click Open to apply state

Given this model, Disconnect is redundant with existing local actions.

Proposal

Remove the Disconnect action and eliminate prContextState = disconnected.

Use only:

• active
• inactive
• closed

Local lifecycle behavior should be:

• Start a new context from Workspaces for repo/local initialization.
• Remove workspace from Workspaces for local deletion.
• Close PR for remote lifecycle change on GitHub.

Why

• Reduces state-machine surface area.
• Removes ambiguous local-only “disconnect” semantics.
• Aligns UI with explicit Open-driven state application.
• De-risks overwrite/merge issues caused by extra transition branches.

Scope

• Remove Disconnect button and handler wiring in PR context UI/workflows.
• Remove disconnectActivePrContext public action path.
• Remove disconnected from supported PR state enum/normalization.
• Remove restore/hydration conditions that special-case disconnected.
• Keep Close PR on GitHub behavior unchanged.
• Keep Workspaces “Start new context for ” behavior as explicit local initialization path.

Data migration

On load/normalize:

• Map persisted prContextState: disconnected to inactive.
• Preserve other metadata fields as-is (repo, head, prNumber, prTitle, tabs).

Optional follow-up:

• One-time rewrite to persist migrated state back to IDB.

Acceptance criteria

• No Disconnect control is rendered anywhere.
• No runtime path writes prContextState = disconnected.
• Existing disconnected records are treated as inactive on restore.
• Switching/opening workspaces works with only active|inactive|closed.
• First-time repo init still works via Workspaces starter option + Open.
• Lint/typecheck pass.
• Playwright suite updated and green after removing disconnected scenarios.

Test updates

• Delete/replace tests for:
  • “Active PR context disconnect uses local-only confirmation flow”
  • “Reopening a disconnected workspace…”
  • all “targetState: disconnected” integrity scenarios
• Add/adjust tests for:
  • starter-context Open flow (no stored contexts)
  • remove-workspace local lifecycle
  • close PR + reopen behavior without disconnected branch
  • cross-repo active/inactive/closed integrity

Docs updates

Update docs to remove disconnected references:

• pr-context-storage-matrix.md
• idb-workspace-state.md

Risks

• Legacy persisted records containing disconnected state.
• Assumptions in tests/helpers expecting disconnected->active restore behavior.

Rollout plan

1. Implement disconnected->inactive normalization and keep backward compatibility.
2. Remove Disconnect UI/action.
3. Remove disconnected branches in runtime/persistence.
4. Update tests/docs.
5. Run full lint/build/Playwright validation.