What does this PR do?

• strips markdown emphasis wrappers around MEDIA: paths before gateway adapters resolve files
• prevents **MEDIA:/tmp/report.docx** from becoming /tmp/report.docx**
• keeps the cleaned user-visible text from leaking raw emphasis markers after media extraction

Related Issue

Fixes #23759

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactor / chore

Changes Made

• expanded BasePlatformAdapter.extract_media() to tolerate markdown emphasis wrappers around MEDIA: directives
• strips trailing * / _ markers from extracted paths as a safety net
• added a regression test covering bold-wrapped media paths

How to Test

• uv run --frozen pytest -q -o addopts='' tests/gateway/test_platform_base.py tests/gateway/test_send_image_file.py -k 'media'
• uv run --frozen ruff check gateway/platforms/base.py tests/gateway/test_platform_base.py
• env -i HOME="$HOME" PATH="$PATH" TERM="${TERM:-xterm-256color}" bash -lc 'cd /Users/leongong/Desktop/LeonProjects/worktrees/hermes-agent/hermes-23759-media-bold-path && uv run --frozen pytest --collect-only -q -o addopts="" tests/gateway/test_platform_base.py tests/gateway/test_send_image_file.py -k media'

Checklist

• I have linked the related issue (or explained why not)
• I added or updated tests for the change
• I ran relevant local verification
• I kept the scope focused
• I ran the full repo test suite

For New Skills

• Not applicable

Screenshots / Logs

• Not applicable