docs(readme): lead with what the pack does for an AI agent, and how to install it

[TMHSDigital]

Closes #370.

Before → after (first screen)

• Tagline. Before: "Skills, rules, snippets, templates, and runnable examples for Blender Python development". After: "Teach Cursor and Claude Code the Blender Python that actually runs on Blender 5.2 LTS and 4.5 LTS."
• Proof line. Three concrete failures the pack prevents, each one measured or fixed in this repo:
  • bpy.context.copy() operator overrides, removed in 4.0 (rule prefer-temp-override-over-context-copy);
  • action.fcurves on 5.x Slotted Actions (snippets: Slotted Actions bridge makes keys that never play back on 4.5 LTS (no slot assigned on the legacy path) #385);
  • Z-up glTF that imports on its back in every engine (snippets: Godot glTF preset exports Z-up, but glTF and Godot are both Y-up #346).
• Claude Code install is shown under the tagline. Cursor and other agents link to Quick start.
• Badges: three rows become one. The drift-check badge is dropped; it is fleet plumbing. The license badge reads CC BY-NC-ND 4.0 + MIT code and links to § License.
• Overview: no longer says Cursor takes skills "by name in chat", which matches fix(distribution): make the Cursor plugin installable and document the install #424.
• .claude-plugin/plugin.json and marketplace.json: the description shown in /plugin is outcome-first and no longer names Cursor inside the Claude UI. Only the description string changed; versions are untouched.
• Not changed here: .cursor-plugin/plugin.json's description, to avoid conflicting with fix(distribution): make the Cursor plugin installable and document the install #424.

Evidence (local)

• python tests/check_counts.py: Counts verified in 5 docs. The counts line and Overview sentence are untouched.
• The Validate "Claude Code packaging" step, extracted and run locally: Claude Code packaging verified.
• build_plugin_dist.py --check: ok.

🤖 Generated with Claude Code

[TMHSDigital]

CI evidence before merge: all checks pass ( 1 pass ). No Blender Smoke run (paths-ignore: docs-only).

[TMHSDigital]

CI evidence before merge: all checks pass ( 13 pass ). Blender Smoke on PR head: Blender 5.2.2 LTS / Blender 4.5.14 LTS. Summaries (happy path; falsifiers) per leg: 143 passed, 1 skipped, 0 failed;143 passed, 0 skipped, 0 failed;141 passed, 3 skipped, 0 failed;136 passed, 7 skipped, 0 failed;

[TMHSDigital]

CI evidence before merge: all checks pass ( 13 pass ). Blender Smoke on PR head: Blender 5.2.2 LTS / Blender 4.5.14 LTS. Summaries (happy path; falsifiers) per leg: 143 passed, 1 skipped, 0 failed;143 passed, 0 skipped, 0 failed;141 passed, 3 skipped, 0 failed;136 passed, 7 skipped, 0 failed;