Add `lint`/`lintFile`/`lintVirtual` exports to `browser.ts` (pre-existing gap)

[dean0x]

Background

packages/mds/src/browser.ts:95 currently exports compile, compileFile, check, checkFile, CheckOptions, and assertKnownKeys — but no lint-related symbols. lint, lintFile, and lintVirtual were added in v0.4.0 (PR #171) and their types were added to types.ts in PR #196, but neither landed a browser.ts export.

Ledger ID: #76 (typescript-browser.ts:95-no_lint_exports)
File: packages/mds/src/browser.ts:95
Originating reviewer: TypeScript (pre-existing; reviewer explicitly said "Separate PR")

Problem

Browser consumers using @mdscript/mds via the WASM backend cannot access lint, lintFile, or lintVirtual. They must import directly from @mdscript/mds-wasm, bypassing the universal wrapper and its option validation (assertKnownKeys).

Note: lintFile may not be meaningful for browser consumers (no filesystem), but lint and lintVirtual are straightforwardly usable with a WASM backend.

Why deferred from PR #196

Pre-existing gap not introduced by PR #196. Adding new browser exports (including potentially 5 new type re-exports) needs its own design decision about which symbols are browser-appropriate, its own test coverage, and possibly an opt-in init() guard on lintFile.

Acceptance Criteria

• browser.ts exports lint, lintVirtual, LintOptions, LintDiagnostic, LintResult (or equivalent types)
• Determine whether lintFile is omitted (no filesystem) or included with a clear note
• @mdscript/mds bundle size assessed (WASM lint bindings are already included; this is a JS-side addition)
• At minimum one browser-path test (existing browser-path smoke tests pattern)

Deferred from: PR #196

[dean0x]

Scope Update: Partial Delivery

Status: 2 of 3 requested exports shipped to the browser entry point.

What Shipped ✓

• lint() — exported and functional
• lintVirtual() — exported and functional

What Was Excluded (Intentionally) ⊘

• lintFile() — deliberately not exported from the browser entry point

Rationale for Excluding lintFile

lintFile() requires filesystem access via node:fs. A browser runtime has no filesystem, so the function cannot work on this entry point. Exporting it would publish a symbol that always fails at runtime, contradicting the overall work's intent (PR #302 also narrowed three published types with basePath?: never to enforce at the type level what the runtime enforces).

Evidence

This is not an oversight:

1. packages/mds/README.md line 53 — Documents that lintFile is absent from the browser entry
2. Test U-BR15 (AC-P3-13) — Explicitly asserts lintFile is not present on the browser entry point with a positive control to prevent vacuous passing
3. Squash commit 4c13ecb — Merged into the integration branch; includes the Closes #215 reference in its body, which will auto-close this issue when the branch merges to main

This comment exists to make the scope reduction explicit before the auto-close, so there is no ambiguity between the title ("export lint, lintFile, and lintVirtual") and what was actually delivered.

Next Steps

Please confirm whether this reduced scope is acceptable, or let us know if lintFile should instead get a browser-appropriate alternative (e.g., a variant taking file content as a string rather than a filesystem path). If a follow-up is needed, please file it as a separate issue and we'll track it there.