Preserve generic form wrapper topology

[chubes4]

Summary

• preserve bounded, source-ordered wrapper ancestry alongside the existing flat form-control contract
• project the provider-neutral topology unchanged into generic/forms/v1
• emit an optional bounded generic/computed-layout-graph/v1 from source CSS cascade facts, including linked stylesheet provenance and conditional media/container/supports variants
• cover real forms, div pseudo-forms, shared wrapper identity, safe presentation hooks, depth and node bounds, and compatibility control references

Fixes #700
Closes #724

A separate pre-existing pseudo-form WordPress site-plan binding-anchor defect discovered during review is tracked in #718.

Verification

• composer validate --strict
• php tests/contract/run.php
• php tests/contract/wordpress-site-plan.php
• php tests/parity/run.php
• composer test
• git diff --check

composer test passed all canonical contracts, 253 parity fixtures, unit suites, and the clean package-install proof.

AI Assistance

OpenAI GPT-5.6 Sol via OpenCode general coding subagent implemented the computed layout graph producer and contract coverage. Chris Huber reviewed and remains responsible for the change.