tasks: phase 61 — what an agent is told before it starts

Runs 55 (the prompt says the run is one turn), then 54 (start_agent
refuses a phase card), then 46 (a board with no runnable commands says
so). No card depends on another; 55 is prompt-only and goes first, 54
and 46 both edit board.html so they run adjacent.

Also the first exercise of the Phases view: 56-59 landed after phase 53
finished, so hiding, the lane, the move refusal and the sweep have not
yet been watched on a live run.

tasks/backlog/61-what-an-agent-is-told-before-it-starts.md

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+# 61 — Phase: what an agent is told before it starts
+
+**Status:** Backlog
+**Priority:** High — every card in it is a hole that has already cost a
+run, and two of them cost one this week
+**Type:** Phase
+
+Three cards about the moment a headless agent is launched: what it is
+allowed to run, what it is told about the run it is in, and what the
+board must refuse to launch at all. They are separate defects with one
+shape — the launch path assumes the agent knows things nobody tells it.
+
+## Cards
+
+- 55 — A headless run gets one turn, and nothing tells the agent that
+- 54 — A work agent must refuse a phase card
+- 46 — A board whose agents cannot run anything says so
+
+## Why this order
+
+None of the three depends on another, so none carries a
+`**Depends on:**` line. The order is editorial and file-shaped:
+
+**55 first** because it touches only the prompt templates and their
+contract test — no overlap with anything, and it is the cheapest to get
+out of the way. **54 and 46 adjacent** because both edit
+`manager/core/board.html`, 54 to distinguish a phase card that has not
+been started and 46 to say when a board's agents have no commands to run.
+Sequencing them means the second starts from a worktree that already has
+the first, rather than colliding in the file this repo edits most.
+
+## What done looks like
+
+- A work prompt that states plainly that the run is one non-interactive
+  turn and that uncommitted work dies with it — the sentence that would
+  have saved card 47's run.
+- `/api/agent/start` refuses a phase card, from a stale tab or by hand,
+  and says **▸ run phase** instead.
+- A board with `BOARD_AGENT_COMMANDS` empty says so once, where a person
+  will see it, instead of letting an agent discover it four minutes into
+  a run.
+
+## Notes
+
+**This is also the first real exercise of the Phases view.** Cards 56–59
+landed after phase 53 finished, so nothing has yet been watched through
+the new arrangement: members should disappear from the Board and appear
+in a lane, the column counts should describe only what is visible, the
+phase card should refuse to move while a member is running, and
+**merge & clean up** should sweep the cards *and* their worktrees and
+branches. Worth watching this one rather than walking away from it, for
+that as much as for the work.
+
+**One thing that looks alarming and is not.** Card 54 changes
+`agents.start_agent`, which is the function the phase runner itself calls
+to launch each member — including the members after it. It cannot break
+the run that carries it: the board runs from the main checkout, and a
+member's changes live in its own worktree until the phase's PR is merged.
+The same is true of 55's prompt edits, which are read fresh from the main
+checkout on every launch.
+
+Card 46's own card notes the trade it comes from: detection replaced the
+install question, so a project the detector does not recognise starts
+with an empty allowlist. That is the honest outcome, and this is the
+card that stops it being a silent one.