ci: restore complete native, Wasm and embedded compatibility checks

[cpunion]

Match LLGo compatibility coverage across Linux/macOS/Windows ABIs, all supported Wasm profiles, and embedded targets. PR checks validate LLGo #2764 at dd08de227; daily and manual runs use their configured ref (main by default).

• Pair Go 1.26 and 1.27 corpus shards and validate report completeness.
• Run ten small core regression jobs before the full GOROOT corpus. Prioritize the observed failures: JS callback exit, threaded WASI panic/recover, large static data, caller lines, allocations, deep recursion, and generated compiler stress. Every selected case must pass.
• Preserve full standard-library and target acceptance matrices, including browser callbacks, Wasm GC/threading, and embedded debugger coverage.
• Retain failed programs for diagnosis and give rangegen-containing Wasm and Intel macOS shards a bounded compiler memory budget. Serialize paired Intel macOS stress builds. Case-specific timeouts remain in LLGo.

Temporary Wasmer PR 3 artifacts are checksum/revision verified. Full qualification of this LLGo commit is pending. No automatic retries or failure suppression are added.