fix(gateway): skip MEDIA: tags inside code blocks and blockquotes

[liuhao1024]

What does this PR do?

Fixes extract_media() false positives where MEDIA:<path> tags inside fenced code blocks, inline code spans, and blockquotes were incorrectly extracted as real media delivery directives. This caused example paths in agent responses to be stripped from user-visible text and potentially delivered as unintended files.

Related Issue

Fixes #35695

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• gateway/platforms/base.py: Added _mask_protected_spans() helper that replaces content inside fenced code blocks, inline code spans, and blockquotes with equal-length whitespace before regex matching. Modified extract_media() to use masked content for both finditer() (extraction) and sub() (cleanup). The helper skips masking backtick-quoted paths in MEDIA: tags (e.g. MEDIA:`/path/to/file.png`) to preserve existing path extraction behavior.
• tests/gateway/test_platform_base.py: Added 5 regression tests covering MEDIA tags in fenced code blocks, inline code, blockquotes, mixed code+prose, and real tags outside protected regions.

How to Test

1. Run pytest tests/gateway/test_platform_base.py -k "TestExtractMedia" -v — all 24 tests should pass (19 existing + 5 new)
2. Verify the false-positive scenario: agent response containing To send an image, include \MEDIA:/path/to/image.jpg`should NOT extract/path/to/image.jpg` as a media file
3. Verify real MEDIA tags still work: MEDIA:/tmp/report.pdf in normal prose should still be extracted
4. Run pytest tests/gateway/test_send_image_file.py tests/gateway/test_media_extraction.py -v — all related tests should pass

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

Code Intelligence

• Analyzed: BasePlatformAdapter.extract_media (callers: ~10 across gateway dispatch paths)
• Analyzed: BasePlatformAdapter._mask_protected_spans (new, called from extract_media only)
• Blast radius: LOW — additive helper, existing extraction paths unchanged
• Related patterns: extract_local_files already uses code-span detection (lines 2753-2761) for the same purpose; this fix applies the same concept to extract_media

[daimon-nous]

Duplicate of #16585 — both fix the same extract_media() false-positive bug on MEDIA: tags inside code blocks. This PR also handles blockquotes and adds tests; #16585 also covers stream_consumer.py. See also #16434 and #35695.

[tonydwb]

Code Review Summary

Verdict: Approved

Overview

Well-crafted fix for extract_media() false positives where MEDIA:<path> tags inside fenced code blocks, inline code spans, and blockquotes were incorrectly extracted as real media delivery directives.

Looks Good

• _mask_protected_spans correctly skips MEDIA: path quotes (e.g. MEDIA:`/path/to/file.png` )
• Preserves character count for offset-valid regex matching
• 5 regression tests covering code blocks, inline code, blockquotes, mixed content, and real tag preservation
• Additive — no changes to existing extraction paths
• Low blast radius; mirrors existing extract_local_files pattern

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Reviewed by Hermes Agent

[liuhao1024]

@daimon-nous[bot] Acknowledged. This PR passes all CI checks, while the competing PR #16585 has a test failure. If maintainers prefer the duplicate flag to take precedence, feel free to close this. Otherwise, I believe this PR is ready for merge.

[kshitijk4poor]

Thanks @liuhao1024 — salvaged into a batch PR alongside the related auto-append guard from #16721: #36275.

Your code-block / inline-code / blockquote masking commit was cherry-picked with authorship preserved; it applied cleanly to current main. Verified together with the other fix — 139 passed, 2 skipped across the gateway media tests, including your new cases.

Closing in favor of #36275.