chore: clear MoonBit v0.10.6 diagnostics and bump CI toolchain pin

[brickfrog]

Housekeeping for the moonc v0.10.5 → v0.10.6 jump. No public surface change — the only .mbti delta is a trailing blank line dropped by the newer moon info (all 10 files show 0 1 in git diff --numstat).

Changes

E0082 ambiguous_braces — 31 sites

Empty {} now warns because it could be an empty map, block, struct literal, or JSON object. Every site was let x : Map[K, V] = {} → Map([]), in otlp/types.mbt, otlp/convert.mbt, flame/flame.mbt, event.mbt, field.mbt, field_show.mbt, env_filter.mbt, span_json.mbt, span_observer.mbt, and id_test.mbt.

Left context.mbt:21 and filter.mbt:20 (ref.val = {}) alone — assignments to an already-typed Ref, not ambiguous, not flagged.

E0020 deprecated try? — 2 sites

Both were let result : Result[_, _] = try? f() immediately followed by guard result is Err(_) else { abort(…) }. The Result never escaped its expression, which is exactly the case the compiler says to rewrite:

try fail_in_scope() catch {
  _ => ()
} noraise {
  _ => abort("expected scoped failure")
}

CI toolchain pin

.github/scripts/setup-moonbit.sh was pinned to 0.10.5+5e7afb0c0, so CI would have verified this branch against a compiler predating the diagnostics it clears. Bumped to 0.10.6+80dc50f24 with recomputed SHA-256 digests for both the toolchain and core archives.

Verification

Ran the pinned installer locally, then the full CI matrix against the resulting isolated MOON_HOME (moonc v0.10.6+80dc50f24):

step	result
moon check native / js / wasm-gc	clean, 0 warnings
moon test --target native	293/293
moon test --target js	280/280
moon test --target wasm-gc	265/265
moon fmt then git diff	no tracked file modified

Also confirmed the 0.10.6 tarball still ships bin/internal/tcc and still does not ship bin/moonx, so the script's chmod and ln -s moon bin/moonx lines remain correct.