fix(grounding): harden native sanitizer and address review nits

[equationalapplications]

Description

Defense-in-depth cleanup for grounding HTML rendering, addressing follow-up items from the PR #472 Copilot review. Hardens the native WebView sanitizer to match the web allowlist behavior, clarifies attribute allowlist logic, and removes an unnecessary wheel listener re-subscription on web.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code refactoring
• Performance improvement
• Test update
• Build/CI update

Related Issue

Follow-up to PR #472 Copilot review feedback.

Changes Made

• Strip <base> tags in the native regex sanitizer alongside <link> and <meta>
• Sanitize img src on the native path using the same isSafeHttpUrl gate as anchor href
• Extract shared stripUnsafeUrlAttribute helper for anchor and img URL attributes
• Refactor isAllowedGroundingAttribute into explicit on* / aria-* / data-* branches
• Change the web scrollport wheel listener effect dependency array from [contentWidth] to []
• Add native sanitizer unit tests for embed tags, resource tags, base tags, and img src validation

Testing

Platforms Tested

• iOS
• Android
• Web

Test Steps

1. npm run typecheck
2. npm run lint
3. npm run test -- --testPathPattern='sanitizeGroundingHtml|groundingShadowContent'

Screenshots

N/A — sanitizer and event-listener changes only; no visible UI change expected.

Before

N/A

After

N/A

Checklist

• My code follows the code style of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

Additional Notes

None of these changes address active critical vulnerabilities; they align native sanitization with the existing web allowlist and close out low-priority maintainability items from the prior review.

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[Copilot]

Pull request overview

This PR tightens defense-in-depth sanitization for grounding HTML rendering, aligning the native regex-based path more closely with the web allowlist sanitizer, and removes an unnecessary wheel-listener re-subscription on web.

Changes:

• Extend native executable-markup stripping to remove <base> alongside <link>/<meta>.
• Add native <img src> URL sanitization using the same isSafeHttpUrl gate as anchor href, factoring shared helper logic.
• Refine the web allowlist attribute check readability and make the web scrollport wheel listener attach only once; add/extend native sanitizer unit tests.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/utils/sanitizeGroundingHtml.ts	Expands native regex sanitizer to strip <base> and sanitize <img src>, extracting shared URL-attribute stripping helper.
src/utils/groundingShadowContent.ts	Clarifies attribute allowlist branching (on* reject, aria-*/data-* allow).
src/utils/tests/sanitizeGroundingHtml.test.ts	Adds tests for additional removed tags and img src URL validation.
src/components/GroundingHtml.web.tsx	Removes unnecessary effect re-run by changing the wheel listener effect deps to [].

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[equationalapplications]

/fix-pr follow-up

Commit: 4c0e2071

Review resolution

• HREF_ATTR_RE / SRC_ATTR_RE word-boundary false positives — Fixed: anchored attribute names to (?:^|\s) instead of \b, added (?:xlink:)? for SVG anchor xlink:href, and made patterns global (gi). (files: src/utils/sanitizeGroundingHtml.ts)
• stripUnsafeUrlAttribute first-match bypass — Fixed: collect all URL-attribute matches, apply last-wins semantics (HTML parser behavior), strip all occurrences when the effective URL is unsafe, collapse duplicates when safe, and preserve self-closing /> syntax on <img>. (files: src/utils/sanitizeGroundingHtml.ts)
• Missing regression tests for edge cases — Fixed: added tests for data-href/data-src non-matching, duplicate href/src with unsafe/safe last values, self-closing img, and xlink:href. (files: src/utils/__tests__/sanitizeGroundingHtml.test.ts)

Verification

• typecheck — pass (npm run typecheck)
• lint — pass (npm run lint)
• tests — pass (npm run test)