Bump the wasmtime pin when wasmtime 48 ships (47.0.3 is current) #1

Status (2026-08-09): BLOCKED ON UPSTREAM — there is nothing to bump to. crates.io max stable for wasmtime-environ is 47.0.3, exactly our pin (verified via the crates.io API during release prep). The two xfail classes below exit only when wasmtime 48 ships with a wasmparser on the ≥0.255 line.

The translator shim pins wasmtime-environ 47.0.3 / wasmparser 0.252. Bumping retires two named xfail classes in the conformance table:

• the 47 wasmparser pin-drift xfails (M2 exit class)
• the 5-entry testgen skew class (wast 255 vs wasmparser 0.252: the 0.253–0.255 window re-arited 🧵 thread opcodes — byte-level desync, see the trap-if-block-and-sync xfail)

Staging, per the C0 ruling (docs/milestones.md row C0):

1. Before/after regression diff with the consumer corpus: tools/smoke-c0 legs 3+4 must stay 9/9 accepted, zero rejections (real polymorph/experiment-mosh artifacts, 2–10.5 MB).
2. Full conformance table compare; only the two named classes above may move.
3. Post-bump: add the optional versionSuffix field to plan import/export entries (the spec's canonical-interface-names 🔗 gate postdates wasmparser 0.252 — see contracts/embedder-api.md, version resolution).

Deliberately an attended task: wasmtime-environ is an internal, unstable API and this is the highest-churn-risk change in the repo (docs/architecture.md §12). Watch the wasmtime release train (monthly); 48 is the trigger.