…e blocks

Skill content injected via slash commands was displayed as the user's
message in the TUI. Now marked synthetic so it is hidden from the UI
but still sent to the LLM. The visible user message shows the slash
command invocation (e.g. /brainstorming create a login page).

Tracks all modifications made in this fork on top of upstream with
commit hashes, files touched, and whether each change is safe to
drop on rebase.

On macOS Sequoia, copying over an existing binary inherits a
com.apple.provenance xattr that causes the OS to SIGKILL the
process on launch from persistent paths like ~/.local/bin.

Remove the `clear` alias from `/new` and add a dedicated `/clear`
slash command that removes all messages and todos from the current
session while preserving the session itself.

Implementation:
- Session.clearMessages service method iterates messages via SyncEvent
- POST /:sessionID/clear server route with assertNotBusy guard
- TUI command with confirmation dialog and abort-if-busy handling
- FORK.md entry tracking upstream PR #19543

Also update upstream-merge skill to check FORK.md for superseded
patches after each merge.

Add a side-channel /ask slash command that lets the user ask the model
a question using the full conversation context, without interrupting
any in-progress turn.

Implementation:
- Hidden "ask" agent with all tools denied and concise system prompt
- SessionPrompt.ask() reads conversation history, calls LLM.stream()
  with tools: {} (same pattern as ensureTitle)
- POST /:sessionID/ask server route — no assertNotBusy, runs
  concurrently with in-progress turns
- DialogAsk TUI component with text input, spinner, and answer display
- /ask slash command registration in session view

Does not persist ask/answer messages to session history (ephemeral).