docs: correct capture examples and RAW conversion semantics

[OskarEichler]

Fixes

Make the high-level snippets valid JavaScript, document omission of captureMode rather than a nonexistent none value, explain WebP/raw results accurately, distinguish binary RAW files from base64 results, separate native capture from Node conversion, preserve the already-PNG fallback, and avoid duplicate file URI prefixes when sharing. Correct CI/test coverage claims: Android Detox is disabled, iOS Detox is non-blocking, several native assertions are best-effort, and the snapshot helper does not compare decoded pixels. Document the actual web artifact names and preserve Linux references.

Compatibility / observable changes

Documentation only. No benchmark guarantee is made. Node conversion uses built-in fs/zlib and the optional pngjs package; these are not React Native built-ins.

Verification

All README JavaScript snippets parse. The Node converter round-trips RAW pixels, preserves an already-encoded PNG, and rejects inconsistent RAW headers.

This patch was applied independently to upstream commit 6acbec50a5e3cab7d668711d757c52cfdc791c76 and passed its targeted external actual-source diagnostics. Across the focused patches, 119 such checks pass. Java/Objective-C diagnostics use controlled bridge/platform doubles or owned filesystem fixtures; they are not substitutes for physical-device rendering tests.

Combined branch checks:

• Existing JS suite: 4 suites, 46 tests pass.
• TypeScript, ESLint (zero warnings), full Prettier check and library build pass.
• Existing Android unit suite: 62 tests pass; Android Debug example build passes.
• Existing Windows managed helper suite: 16 tests pass on .NET 8.
• Unsigned iOS Simulator example build passes. Native tests: 13/14 pass; the one intentional old-behavior assertion conflict is described below.
• Android and iOS production Metro bundles pass. Web production build passes with three bundle-size warnings.
• React 18.3.1: all 21 applicable JS diagnostic controls pass; React 19 includes callback-ref cleanup coverage.

The separate iOS cleanup patch intentionally makes the existing test named testReleaseCapture_currentlyDeletesPrefixOnlyImposterDirectories_KNOWN_LOOSE_GUARD fail because it asserts the unsafe old behavior. That patch is kept in a separate draft PR. No checked-in test/spec or snapshot files were added, modified, regenerated or disabled.

Windows/Expo native builds, physical-device video/PixelCopy output, and full Detox suites were not run. The full unchanged Playwright suite was run against both baseline and patched builds: both have 9 passes and the same 3 failures. Two Linux-reference screenshot mismatches have byte-identical baseline/patched actual images on macOS. The CORS fixture hard-codes port 3000, occupied by an unrelated local backend; the isolated example uses another port. No snapshots or assertions were changed. React Doctor also reports existing example suggestions and a React-18 ref-cleanup warning; the latter was checked against actual React 18 legacy-ref and React 19 cleanup behavior. No rules were suppressed.

Scope

• README.md
• src/index.tsx
• example/e2e/README.md
• example-web/README.md

Unrelated audit changes are submitted separately.