Rework README first screen for discoverability

[Cyning12]

Summary

Rewrote the top section of README.md (and README.zh-CN.md) to make SpecWave's value proposition immediately clear to developers landing from external discovery sources (Hacker News, Reddit, awesome lists, HelloGitHub).

What Changed

Top Section (First Screen)

• Added: Clear one-line value prop: "Write your AI coding rules once. SpecWave installs them natively into Cursor, Claude Code, Copilot, and 10 more tools."
• Added: npm version and license badges
• Added: Problem/solution comparison table showing the manual pain point vs. SpecWave's single-command approach
• Added: Compact 13-host support table with what files are generated for each tool
• Moved: Quick start section higher (after problem/solution)
• Added: Plain-language "Why fail-closed gates?" section explaining exit codes without jargon
• Added: TODO placeholder for terminal demo (recording tools not available in build environment; marked clearly rather than faking)
• Added: Gentle star request at end of top section: "If this saves you time, a ⭐ helps others find it."

Structure

• Kept all existing deep documentation (core concepts, detailed CLI commands, advanced features)
• Reorganized flow: value prop → problem → solution → quick start → supported hosts → gates → features → installation → deep dive
• Both English and Chinese READMEs updated with consistent structure

Verification

All claims verified against actual code:

• 13 hosts confirmed from assets/ide/host-adapt/examples/mvp-hosts.yaml
• Generated file paths confirmed from host-adapt README
• CLI commands verified against actual CLI implementation

TODO (Left for Future)

• Terminal demo: Add real recording (GIF/SVG) when vhs or asciinema is available. Placeholder marked clearly in README with HTML comment. Should show: npx spec-wave host apply --tools cursor,claude --yes → native files generated → verify gate check flow.

Rationale

The current README opens with internal concepts ("adapt table", "P0 gates", "Harness", "ICVO") that newcomers don't understand. This causes:

• Visitors bouncing without understanding what the tool does
• Zero stars despite promotion post views (per user context)

The new structure:

1. 10-second clarity: Plain language, immediate value, concrete before/after comparison
2. Show don't tell: Table of 13 tools + what files are generated (not abstract "multi-host")
3. Build trust: Badges, real examples, verified claims, no invented features
4. Lower friction: Quick start before deep concepts

Testing

• Both README.md and README.zh-CN.md updated
• All links functional (internal doc links preserved)
• All claims verified against source code
• No breaking changes to existing deep documentation
• Consistent structure between English and Chinese versions

Related

• Addresses the discoverability problem mentioned in user context (promotion posts got views but zero stars)
• Complements existing documentation rather than replacing it
• Makes the GitHub landing page work harder for organic discovery