WebAssembly exceptions/tail calls: upstream corpus, CI, and terminal evidence

Parent: #266 Depends on: #288, #289, #290, #291 Roadmap: #268, #142, #134

Publish the auditable completion gate for both pinned profiles.

Acceptance:

• Extend the exact-pin WAST runner and inventory schema for exception/tail-call commands and execution modes with zero hidden filtering.
• Run every declared upstream file and publish pass/fail/not-applicable/runner-error totals plus per-file accounting.
• Add bounded pin/drift/behavior CI witnesses and deliberate complete-run commands.
• Pass deep tail-stack, nested exception, JS identity, precise-GC, lifecycle, leak, stress, and sanitizer gates across supported hosts.
• Document host/architecture boundaries, reproduction, and any equivalent system-engine comparison in README and WebAssembly docs.

Completed in 0429297, b2d3f24, e9fdc5a, deb27a6, and 894d22a. All six declared proposal files and 205 commands are accounted for: tail calls 108 pass + 11 explicit text-only N/A; exceptions 84 pass + 2 explicit text-only N/A; zero failures and zero runner errors. The ordinary CI feature verifier locks proposal/WABT pins, file sets, per-file totals, every execution mode, and the sole N/A reason. Focused runner regressions, deep tail/exception, precise-GC, leak, lifecycle, ThreadSanitizer, and the 10-row system-JSC boundary evidence are documented with complete reproduction commands and host limits.