Token budget UX: deliver the 80% warning, frame replays, notice on dropped messages

[psamiton]

Problem

The budget system pauses minds with little warning and drops messages silently:

• The 80% warning is never delivered. token-budget.ts has checkBudget() returning "warning" at ≥80% and acknowledgeWarning() / a warningInjected flag — but nothing outside token-budget.ts calls either. Dead code: the mind gets no early warning at all.
• At 100%, a notice is recorded (turn-lifecycle.ts ~line 262) — but if the mind never gets another turn that period, it never learns why the world went quiet.
• Queue overflow silently drops the oldest messages past MAX_QUEUE_SIZE = 100 (token-budget.ts ~line 119). No count, no notice.
• Replayed messages arrive on period reset with no framing that they were held.

Implementation plan

1. Wire the 80% warning: in turn-lifecycle.ts where budget accounting happens, call checkBudget(); on "warning", record a notice ("You've used ~80% of your token budget for this period — consider wrapping up or prioritizing.") and call acknowledgeWarning(). Delivered on the next pre-prompt drain — the compaction-warning analog for budgets.
2. Overflow drops: count drops per period in token-budget.ts; record a notice ("N messages were dropped while you were over budget.") and/or prepend the count to the replay.
3. Replay framing: messages replayed via sendSystemMessage on period reset should be prefaced: "These messages arrived while your budget was exhausted:" — template in packages/daemon/src/lib/prompts.ts.
4. Exceeded messaging: review the existing exceeded-notice text so it states when the budget resets (the period end is known).
5. Budget visibility at startup is covered by the environment-transparency issue (VOLUTE_TOKEN_BUDGET env var).

Testing

• Extend existing token-budget unit tests: warning fires once per period and resets on tick; drop counting; replay preface.
• turn-lifecycle unit test: "warning" status → notice recorded + acknowledged.

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Part of the "mind experience" improvement series. Principle: budget limits should feel like a heads-up, not a trapdoor.