fleet crew deploy: BAD_REQUEST 'empty prompt' even though mission prompt is populated

[khang859]

Bug Description

Component: fleet crew deploy
Summary: crew deploy rejects a mission with BAD_REQUEST: Mission has an empty prompt even though fleet missions show clearly displays a populated prompt for that mission.

Environment

• Fleet Starbase: starbase-b20842
• Sector: fleet
• OS: macOS Darwin 25.2.0

What Happened

After creating a research mission via fleet missions add, fleet missions show <id> displays the full prompt correctly. But calling fleet crew deploy --sector fleet --mission <id> returns:

Error: Mission 3 has an empty prompt. Update it first:
  fleet missions update 3 --prompt "..." (BAD_REQUEST)

Running fleet missions update 3 --prompt "..." with a new prompt succeeds and missions show again shows the updated prompt — but crew deploy still returns the same error.

The mission was created with a multi-line prompt containing markdown (##, numbered lists, backticks).

Expected Behavior

fleet crew deploy should read the persisted prompt and deploy the crew successfully.

Steps to Reproduce

1. fleet missions add --sector fleet --type research --summary "..." --prompt "<long multi-line markdown prompt>"
2. Confirm prompt appears: fleet missions show <id> — prompt is visible
3. fleet crew deploy --sector fleet --mission <id> → BAD_REQUEST: empty prompt
4. fleet missions update <id> --prompt "<new prompt>" — succeeds
5. fleet missions show <id> — new prompt is visible
6. fleet crew deploy --sector fleet --mission <id> → same BAD_REQUEST: empty prompt

Error Messages

Error: Mission 3 has an empty prompt. Update it first:
  fleet missions update 3 --prompt "..." (BAD_REQUEST)

Hypothesis

The prompt may be stored but not being read correctly by the deploy endpoint — possibly a whitespace/encoding issue with multi-line strings passed via CLI arguments, or the deploy endpoint reads from a different field/cache than missions show.

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Reported via Admiral interface