fix: simplify extension description for clarity

[lcomplete]

Summary

• Shortened the browser extension description for better clarity and conciseness
• Removed redundant feature mentions (key points extraction, immersive article preview) that made the description too long

Test plan

• Verify manifest.json is valid JSON
• Confirm extension loads correctly with updated manifest

🤖 Generated with Claude Code

[augmentcode]

🤖 Augment PR Summary

Summary: Shortens the browser extension description in the MV3 manifest to improve clarity and keep the text concise.
Changes: Removes redundant feature mentions from the description field while preserving the core feature set.

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