docs(readme): redraw the front half for newcomers after 1.0

[MendixMau]

The README front half was text-heavy and predated most of 1.0. This redraws it for someone landing on the repo for the first time. Reference and the generated routing blocks are untouched.

• Diagram of where the toolkit sits (you, the agent, toolkit, mxcli, the app, reports)
• The measured 1.0 numbers: 5 of 5 vs 0 of 5 bad-binding refusals, ~40% fewer tool calls with context packs, 0 to 1 of 20 journeys per change
• The pipeline as three phases (Understand, Design, Build and ship) with the hard gates
• A pieces table and a new What you see table: process map and BRD report, progress report, dashboard, bug log
• Short sections for modes, quick start, settings (links the 1.0 settings table), testing, input, bundled releases
• The earlier detail is kept behind <details> folds, nothing removed

Reader-visible words above Reference: about 1,900 → about 530. Rendered and checked locally with GitHub's markdown API plus Mermaid.

Impact

Always-loaded text	none
Routed skills	none
Scripts	none
Sync behaviour	none
Consumer action	none

render-routing --check, check-skill-routing, tests/run-tests.sh (33/33), PR discipline and the leak guard pass.

🤖 Generated with Claude Code