doc-tests: the three fastify snippets cannot run under PERRY_NO_AUTO_OPTIMIZE — excluded to unblock the release gate (coverage gap)

[proggeramlug]

Three doc-example snippets are COMPILE_FAIL in doc-tests, which gates the release:

• docs/examples/getting-started/npm_packages.ts
• docs/examples/stdlib/http/fastify_json.ts
• docs/examples/stdlib/overview/snippets.ts

All three import 'fastify', and all three fail with the same deliberate hard error:

error: `import 'fastify'` is not supported with PERRY_NO_AUTO_OPTIMIZE: the prebuilt stdlib is
not compiled with `external-fastify-pump`, so fastify requests would never drain (the request
loop hangs).

This is a harness/config incompatibility, not a compiler bug. scripts/run_doc_tests.sh sets PERRY_NO_AUTO_OPTIMIZE=1 for host runs — a large speed win (~30–200 s saved per test, ~80% of doc-tests wall time) — and the guard in optimized_libs/driver.rs correctly refuses to build a fastify binary that would hang at runtime.

Note the guard keys on the environment variable alone; it does not inspect the archive. I verified that building perry-stdlib-static --features perry-stdlib/external-fastify-pump does not satisfy it, so "just enable the feature in the prebuild" is not a fix on its own.

Interim (PR #8476): exclude the three snippets from the no-auto run, on the same terms as stdlib/http/snippets.ts which is already excluded for a sibling reason. This unblocks the release gate. It is an explicit coverage gap — those three snippets are no longer verified by CI at all, and this issue exists to close it.

Proper fix, pick one:

1. Second pass — have run_doc_tests.sh collect the fastify-importing snippets and run just those without PERRY_NO_AUTO_OPTIMIZE, paying the rebuild cost for three tests instead of losing coverage. Probably the best value.
2. Self-describing skip — extend the harness's existing banner mechanism (// platforms:) with something like // requires: auto-optimize, so the constraint lives in the file rather than in a workflow string, and shows up as a reported SKIP rather than silence.
3. Make the guard evidence-based — have it inspect the stdlib archive for the pump symbols instead of assuming from the env var, so a prebuild that does include external-fastify-pump is accepted. Combine with adding the feature to the doc-tests prebuild.

Option 2 also fixes a smaller wart: an exclusion in a workflow string is invisible to anyone reading the snippet, which is how this class stayed unnoticed while the full tier was dark.

[proggeramlug]

Fixed by #9820, landed on main via merge train #9866. The train merged as its own branch, so the close-keyword never fired — closing manually.