T05: live cost budget replaces the dead token budget

The 8k/10k per-task token budget was never referenced or enforced and
T08 blew past it silently. Replaced with a budget that can actually
fire.

The design constraint is the interesting part: per-task cost needs the
commit that CLOSES the task, so a per-task budget is unavoidably
retrospective -- it can only report a breach after the money is spent,
which is the dead-policy failure again. What IS observable mid-task is
spend since the last commit, because the transcript is append-live. So
the budget binds on the open remainder.

  CB-01  budget = USD since the last commit, via `make cost-budget`
  CB-02  soft $10.00 (state progress, decide), hard $22.00 (stop)

Calibrated on the 32 non-empty commit intervals of CB-WP-0001: p50
$1.40, p90 $9.36, max $10.80. Soft sits just below the observed maximum
-- it would have fired exactly once on the calibration pass. Hard is ~2x
the observed max, a value never reached in 32 intervals, so reaching it
means the session is doing something the data has no example of.

Both thresholds are set ABOVE every observed value, so they bind on
future work rather than ratifying present work -- the distinction T07
is about.

Stated limit: it is a command, not a daemon. An agent that never runs it
gets no signal, which is the dead-policy failure one level up. Mitigated
only by being free to run and on the one command surface.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

specs/InnerLoop.md

@@ -317,6 +317,16 @@ The loop exists to be driven by agents. Therefore:
    that does not exist. Replacement in USD is CB-WP-0003 T05; until then
    this is documentation of a gap, not a rule.
 
+6a. **Live cost budget** *(replaces the above)* — spend since the last
+   commit, soft **$10.00**, hard **$22.00**, checked by `make cost-budget`.
+   Calibrated on the 32 commit intervals of CB-WP-0001 (p50 $1.40, p90
+   $9.36, max $10.80), so both thresholds bind on future work rather than
+   ratifying past work. Contract: [CostAccounting.md](CostAccounting.md)
+   §7 (CB-01, CB-02). It fires on the open remainder rather than per task
+   because per-task cost needs the commit that closes the task, and a
+   budget that can only report after the money is spent is the dead policy
+   this replaces.
+
 **Enforcement status.** Rules above that a command can check are enforced
 by `make loop-lint`; the full classification of every InnerLoop rule as
 executable / checkable / decorative, with the failure class each catches,