Security: prevent UI-only mutation affordances from bypassing host authorization

[marcello-tk]

Parent security issue: #109
Umbrella: #108

Problem / exposed surface

The Worklist, Commits, Issues, and helper surfaces can present buttons or helpers that suggest a mutation: approve, drop, commit, push, close issue, send text to the terminal, or open external URLs. The UI is useful for deliberate user action, but it should not be the policy authority.

The risk is a UI path that looks authorized because a button is enabled or a helper function is available, while the host-side route or IPC command does not independently verify the required approval state.

Relevant surfaces:

• app/tools/components/Workspace.xmlui
• app/__shell/helpers.js
• Worklist approval / iterate / drop buttons
• Commits tab push helper
• Issues tab close/comment/create flows
• host routes and IPC commands called from those helpers

Proposed change

Audit UI mutation affordances against host-side authorization checks:

• List every UI action that changes disk, git state, GitHub state, terminal state, or approval state.
• For each action, identify the host-side check that makes the action legal.
• Move policy decisions out of frontend-only enabled/disabled state where needed.
• Keep frontend state useful for user feedback, but make the host the final decision point.

Acceptance criteria

• Every mutating UI affordance has a matching host-side policy check or an explicit rationale for why it does not need one.
• Frontend disabled state is treated as UX, not as the security boundary.
• Documentation names the sensitive helper functions and the host routes/IPC commands that enforce their permissions.