Source-map cosmetic/consistency nits (TS-1, TS-2, CON-2, CON-4, CX-6, PY-2)

[dean0x]

Follow-up cosmetic / consistency nits surfaced during the PR #183 source-map review. No defects — type-safety polish, doc niceties, and test-style consistency deferred out of the merge-ready branch.

Items

• TS-1 — packages/mds/src/util/options.ts:27 — redundant as CompileOptions casts; remove now-unneeded assertions. Type-safety polish.
  → LANDED in PR v0.4.0 Wave 1: breaking changes, live-bug fixes, and release-safety gates #308 (339df37). grep -rn "as CompileOptions" packages/mds/src/ → zero hits. Cast-free replacement is forwardOpts at packages/mds/src/util/options.ts:296-317, with METHOD_KEYS.compile now keysOf<CompileOptions>(...) instead of keysOf<_CompileBackendOpts>.
• TS-2 — packages/mds/src/backend/native.ts:87 — redundant downcasts on the compileOpt() return. Cosmetic.
  → LANDED in PR v0.4.0 Wave 1: breaking changes, live-bug fixes, and release-safety gates #308 (339df37). Old form at 113f472:packages/mds/src/backend/native.ts:88 was compileOpt(options) as NapiCompileOpts | undefined (twin at :100). Current native.ts:83 is addon.compile(source, forwardOpts(options, 'compile')). grep -n "as Napi" native.ts and grep -rn "compileOpt(" packages/mds/src/ → zero hits. Note compileOpts (plural) at packages/mds/src/backend/wasm.ts:353 is a separate local WASM helper, not this.
• CON-2 — (test files) — divergent test-ID schemes across suites (F-SM / SM-PY / U-SM). Cosmetic; arguably intentional per-backend namespacing — reconcile or document the convention. (Updated refs: crates/mds-napi/__test__/index.spec.mjs:1211 (F-SM*), crates/mds-python/tests/test_source_map.py:4-13 (SM-PY-*), packages/mds/__test__/source-map.spec.mjs:5-12 (U-SM*), plus a fourth scheme sm1_..sm20b in crates/mds-cli/tests/cli_source_map.rs.)
• CON-4 — crates/mds-wasm/src/lib.rs:191-193 (struct), :394-398 and :740-742 (round-trip), :441-442 (unpack) — WASM CompileOptions uses a two-bool round-trip; align the API shape with the other bindings. Cosmetic API-shape consistency.
• CX-6 — crates/mds-core/src/sourcemap.rs — the S3/S6/S7/S8/S9 provenance legend is absent; add the provenance-tag legend as a doc comment. Doc nicety, no defect. Note (reference check, 6d41777): the tag S9 has zero occurrences in crates/mds-core/src/. S3/S6/S7/S8 appear as inline comments at sourcemap.rs:28, 594, 597, 604, 655, 690, 841, 846. The legend is genuinely absent, but the tag vocabulary this issue asks for is partly stale — flagged, not resolved.
• PY-2 — crates/mds-python/tests/test_source_map.py:27 — module-scope FIXTURES instead of pytest fixture injection. Test style.

---

Deferred from code review of PR #183 (#62); see resolution-summary 2026-07-16_1241.

---

References verified against main at 6d41777 (2026-08-26). Line numbers corrected; scope and acceptance criteria unchanged.