docs: catch up README/ROADMAP/ARCHITECTURE with v1.8.0–v1.9.x

[artyomsv]

Audit of user-facing docs against shipped releases since v1.7 found multiple stale references and missing entries. This commit closes the gap; every change is doc-only.

README:

• MCP tool count 15 → 17 (M12 added 2, M13 added 2)
• New feature sections: memory reporting, notification center, client/daemon version handshake, claude-code session-id rotation
• Keybinding table gains F1, F3, Alt+N, Alt+Backspace, Ctrl+S
• Roadmap table adds M13 + v1.8.0 + v1.9.1 + v1.9.2 + soft-wrap rows

ROADMAP:

• MCP tools list expanded to 17 with Phase A/B + M12 + M13 breakdown
• New sections for M13 memory reporting, v1.8.0 version handshake, v1.9.1 VT drain + Update watchdog, v1.9.2 claude SessionStart hook, and notes soft-wrap

ARCHITECTURE:

• ADR-5 rewritten — SQLite was never used; the actual layout is TOML config + JSON state + per-pane binary ghost buffers + plain text notes/sessions/mcp-logs
• Five new ADRs: ADR-20 version handshake, ADR-21 memory reporting, ADR-22 VT-emulator drain + Update watchdog, ADR-23 claude SessionStart hook, ADR-24 TextEditor soft-wrap visual layout
• Storage layout adds claudehook/ + sessions/ directories

VISION:

• JSON Transformer tagged "Status: Planned" (was unmarked)
• Tech-requirements row drops the SQLite reference
• New Pillar F "AI-Orchestration Layer (MCP)" — the strategic differentiator was missing

PRD:

• Post-M5 milestones table — M6/M7/M8/M10/M12/M13 stubs link to ROADMAP + per-feature design docs

plugin-reference:

• [plugin] table documents schema_version
• [command] env row documents the QUIL_PANE_ID injected env var

site:

• features.ts / faq.ts / index.astro: 15 → 17 MCP tools
• faq.ts: ghost buffers stored in binary files, not SQLite
• features.ts: new memory-reporting + version-handshake feature cards