release(v2.2.0): arrange and save the ERD layout

[ikelaiah]

Summary

• Adds deterministic Auto arrange to the ERD page: layered parent→child flow with bounded barycenter crossing reduction, cycle-safe ordering, and views placed downstream of the tables referenced in their FROM/JOIN clause (declared layout hint only).
• Adds band wrapping so wide/tall estates become readable: 800-table chain 3,192×16,208 and 799-leaf fan 3,192×11,480 instead of 217k-wide/128k-tall strips; layout ~53 ms / ~5 ms, zero overlaps.
• Adds layout saving: opt-in Save/Restore/Forget in this browser, plus versioned Export/Import JSON keyed by a schema fingerprint (unmatched entities appended, never overlapped or dropped).
• Reworks the canvas to absolute positions so dragged cards persist across re-renders, edits, Compact mode, and saved layouts; Reset returns to declaration order.
• Release prep: version 2.2.0, CHANGELOG, docs/releases/v2.2.0.md, docs/metrics-v2.2.0.json.

Test plan

• npm run typecheck, npm run build, npm run test:file, npm run metrics
• Golden browser suite tests/index.html: 220/220 (schema suite 29/29 including 7 new layout fixtures: determinism, overlap-free, parent-before-child, view sources, file round-trip/rejection, 300-table bulk)
• UI suite (served): 31/31; security suite: pass
• 800-table page smoke: banded stage, 800 cards, Fit 5%, zoom-correct drag, save → auto-arrange → restore round-trip
• npm run package:smoke: procflow-v2.2.0.zip structure and local-file startup pass

Notes

• Auto arrange is deterministic near-optimal, not a minimum-crossing guarantee.
• Layout is UI state: it does not affect analysis, Mermaid export, or the workspace snapshot.