docs: CHANGELOG for PTY transcript pricing (Unreleased)

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

CHANGELOG.md

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 ## [Unreleased]
 
-**The train gate's paid report now prices the trials it used to call "cost unknown".** 32 of 139 gate trials had no cost on every gate since Oct 26, so the report's total understated a gate by about $7.50 (GSTA-150 audit). Three of the four causes are fixed here; PTY sessions follow in the next PR.
+**The train gate's paid report now prices the trials it used to call "cost unknown".** 32 of 139 gate trials had no cost on every gate since Oct 26, so the report's total understated a gate by about $7.50 (GSTA-150 audit). All four causes are fixed.
 
 ### Fixed
 - **Label-named records in multi-case shards** (`test/helpers/e2e-helpers.ts`, `scripts/lib/paid-report.ts`): a `claude -p` record named by its display label ("browse basic commands") carries `cost_case_id` from `runSkillTest`'s registered test name, and the report binds its cost to that case. The failed record, failure class and model still come from the records named by case id, so no verdict, class or pass-rate series changes (22 trials: bws, session-intelligence, workflow, skillify, review-attribution, review, gate-integrity, diagram).
 - **Aborted Agent SDK sessions** (`test/helpers/agent-sdk-runner.ts`, `lib/pricing.ts`): a session that ends without a result event logs its streamed usage as `streamed_cost_usd` in the session ledger, priced once per message id at its largest output, subagent turns included, with 5-minute cache writes at 1.25x and 1-hour writes at 2x input. An unpriced model leaves the cost unknown (auq-format-gate).
 - **Model-free cases**: `timeline-event-flow` runs no model, so with no record and no session it is a known $0. A test checks every listed case's body starts no model session.
+- **PTY sessions** (`test/helpers/pty/launch.ts`, `test/helpers/pty/session.ts`, `test/helpers/pty/transcript-cost.ts`): the hermetic launcher pins a random `--session-id` when the caller passes none and is not resuming, and each PTY ledger row prices that session's transcript (`projects/*/<id>.jsonl` plus its `subagents/` files) as `streamed_cost_usd`. No transcript, no usage or an unpriced model leaves the cost unknown, never $0, and a read error never reaches the test. This covers 8 cases and 14 sessions per gate: plan-mode-no-op, plan-design-with-ui-scope, the plan-ceo and plan-devex finding-floor and plan-mode cases, autoplan-guard-pty and office-hours-auto-mode. Checked live, a `claude -p` session with one subagent priced $0.090376 from its transcripts, equal to its `total_cost_usd`.
 - **The headline total** adds session cost that no collector record carries, so newly priced trials reach the gate's `cost $X` line exactly once.
 
 ### Tests
-- `test/paid-report-cost.test.ts`: pricing arithmetic, streamed dedupe, `caseCost`, `recordE2E`'s `cost_case_id`, a two-case shard whose label-named records bind by cost without changing the failed record, class or model. `test/paid-report-census.test.ts`: a record-less trial's streamed cost reaches the trial and the verdict total once.
+- `test/paid-report-cost.test.ts`: pricing arithmetic, streamed dedupe, `caseCost`, `recordE2E`'s `cost_case_id`, a two-case shard whose label-named records bind by cost without changing the failed record, class or model. `test/paid-report-census.test.ts`: a record-less trial's streamed cost reaches the trial and the verdict total once. `test/helpers/pty-transcript-cost.unit.test.ts`: a session, its inline sidechains and subagent files priced once per message id; a foreign session, missing or unreadable transcript, or unpriced model stays unknown. `test/helpers/claude-pty-runner.launch.unit.test.ts`: one pinned session id, a caller's id kept in either form, none when resuming or non-hermetic.
 
 ## [1.91.304.0] - 2026-10-29