ci(image): pin Claude Code 2.1.284, the version users run

Request-body capture shows both 2.1.251 and 2.1.284 send effort "high" to
claude-fable-5-1; 2.1.284 adds the model's own profile. The slower 2.1.284
census was mostly API latency: its SDK-only judges were 25% slower too. Nine
previously slow cases pass on 2.1.284 within unchanged budgets.

CHANGELOG.md

@@ -41,7 +41,7 @@ Run `bun run typecheck` and `bun run typecheck:test` before you push; both are f
 - Paid evals: one test file or case per machine within a 540-second slice budget, planned from recorded per-tier and per-case durations; case sharding for plan, design, review-army, shared-libs, shared-libs-paths, ship-docsync and qa-callers.
 - Verdict policy: no retries; `rule` cases fail on any failed trial, `behavior` cases pass on 2 of 3 parallel trials with contract assertions still strict, `judge` entries average 3 samples against unchanged thresholds. One panel-verdict function feeds the report, PR comment, weekly issue and pass-rate history. A census whose every red is infrastructure is re-dispatched once, and both runs are reported.
 - New non-blocking weekly `evals-marathon.yml` lane for full start-to-finish flows: the full `/office-hours` workflow (a focused design-draft case replaces it in the weekly lane) and the full `/plan-ceo-review` split-overflow run, which took 8 to 20 minutes on its own.
-- The CI image stays on Claude Code 2.1.251. On 2.1.284, sessions ran 20% longer on the same model (per-turn effort) and 11 gate cases timed out on unchanged budgets; that bump needs its own budget work.
+- The CI image pins Claude Code 2.1.284, the first version that recognizes the eval model `claude-fable-5-1` and runs it with the same profile users get. Both versions send effort "high"; a census that looked slower on 2.1.284 was mostly slower API responses (its SDK-only judges, which never start the CLI, were 25% slower too), and nine previously slow cases pass on 2.1.284 within unchanged budgets.
 - `lib/cso/*.ts` is formatted with pinned Prettier; minified transpile output is byte-identical except three canonicalized regex flag orders.
 - The duplicate dispatch-only `ship-docsync` case is removed; `ship-docsync-completion` asserts the same on the same fixture.