fix(preview): restore canon root resolver for normative layout

[transitrix]

Summary

Restores the catalogue-root resolver that was accidentally deleted in PR #603 (Gradle wrapper integrity pin). The resolver determines where the canon/ directory is located, which is needed for preview rendering to find canonical elements and relations.

The fix restores two key functions:

• findModelRootPath() — locates the adopter manifest (transitrix.yaml)
• findCanonRootPath() — resolves canon/ relative to the model root (normative layout), with fallback to the legacy walk-up-for-basename-canon (backward compatibility)

Also restores the two unit tests that verify both layouts work correctly. These tests are load-bearing — without them, a future merge could accidentally delete the walker again without failing CI.

Test plan

• ✅ All 27 canon-loader unit tests pass
• ✅ Normative layout test: resolves canon/ via transitrix.yaml
• ✅ Legacy layout test: still resolves via ancestor directory named canon

Acceptance

• ✅ Opening a projection under views/<notation>/ with transitrix.yaml and canon/ as siblings resolves the catalogue
• ✅ Files under canon/elements/ still resolve (legacy layout)
• ✅ Tests fail CI if the resolver is deleted without also deleting the tests
• ✅ All nine preview modules share this single function (no fork)

Fixes transitrix-hq#485.

🤖 Generated with Claude Code

[github-actions]

📊 Metrics Regression Report

✅ All metrics within tolerance

Summary

• Diagrams tested: 9
• Successful: 9
• Failed: 0
• Violations: 0

Details

ai-expense-approval.bpmn.transitrix.yaml

Metric	Baseline	Current	Delta	Status
crossings	1	1	0.00	✓
bends	6	6	0.00	✓
edgeLength	1868	1868	0.00 (0.0%)	✓
waypointDensity	2.6	2.6	0.00 (0.0%)	✓
spineDeviation	0	0	0.00	✓
emptyArea	0.48125	0.48125	0.00	✓
portViolations	0	0	0.00	✓

feature-release.bpmn.transitrix.yaml

Metric	Baseline	Current	Delta	Status
crossings	1	1	0.00	✓
bends	13	13	0.00	✓
edgeLength	3428	3428	0.00 (0.0%)	✓
waypointDensity	3	3	0.00 (0.0%)	✓
spineDeviation	0	0	0.00	✓
emptyArea	0.5500909090909091	0.5500909090909091	0.00	✓
portViolations	0	0	0.00	✓

large-cyclic-workflow.bpmn.transitrix.yaml

Metric	Baseline	Current	Delta	Status
crossings	2	2	0.00	✓
bends	28	28	0.00	✓
edgeLength	7479	7479	0.00 (0.0%)	✓
waypointDensity	3.12	3.12	0.00 (0.0%)	✓
spineDeviation	66	66	0.00	✓
emptyArea	0.793134974640294	0.793134974640294	0.00	✓
portViolations	1	1	0.00	✓

order-fulfillment.bpmn.transitrix.yaml

Metric	Baseline	Current	Delta	Status
crossings	0	0	0.00	✓
bends	2	2	0.00	✓
edgeLength	728	728	0.00 (0.0%)	✓
waypointDensity	2.3333333333333335	2.3333333333333335	0.00 (0.0%)	✓
spineDeviation	0	0	0.00	✓
emptyArea	0.5622894736842106	0.5622894736842106	0.00	✓
portViolations	0	0	0.00	✓

parallel-tracks.bpmn.transitrix.yaml

Metric	Baseline	Current	Delta	Status
crossings	0	0	0.00	✓
bends	6	6	0.00	✓
edgeLength	2104	2104	0.00 (0.0%)	✓
waypointDensity	2.6666666666666665	2.6666666666666665	0.00 (0.0%)	✓
spineDeviation	33	33	0.00	✓
emptyArea	0.6834468042259194	0.6834468042259194	0.00	✓
portViolations	0	0	0.00	✓

simple-approval.bpmn.transitrix.yaml

Metric	Baseline	Current	Delta	Status
crossings	0	0	0.00	✓
bends	8	8	0.00	✓
edgeLength	1450	1450	0.00 (0.0%)	✓
waypointDensity	3.142857142857143	3.142857142857143	0.00 (0.0%)	✓
spineDeviation	33	33	0.00	✓
emptyArea	0.7764882411250177	0.7764882411250177	0.00	✓
portViolations	0	0	0.00	✓

simple-linear.bpmn.transitrix.yaml

Metric	Baseline	Current	Delta	Status
crossings	0	0	0.00	✓
bends	0	0	0.00	✓
edgeLength	440	440	0.00 (0.0%)	✓
waypointDensity	2	2	0.00 (0.0%)	✓
spineDeviation	0	0	0.00	✓
emptyArea	0.5258771929824562	0.5258771929824562	0.00	✓
portViolations	0	0	0.00	✓

small-dense-approval.bpmn.transitrix.yaml

Metric	Baseline	Current	Delta	Status
crossings	0	0	0.00	✓
bends	14	14	0.00	✓
edgeLength	2066	2066	0.00 (0.0%)	✓
waypointDensity	3.272727272727273	3.272727272727273	0.00 (0.0%)	✓
spineDeviation	33	33	0.00	✓
emptyArea	0.8091206777597997	0.8091206777597997	0.00	✓
portViolations	0	0	0.00	✓

xlarge-stress-test.bpmn.transitrix.yaml

Metric	Baseline	Current	Delta	Status
crossings	0	1	+1.00	✓
bends	62	64	+2.00	✓
edgeLength	11526	11674	+148.00 (1.3%)	✓
waypointDensity	3.1481481481481484	3.185185185185185	+0.04 (1.2%)	✓
spineDeviation	132	132	0.00	✓
emptyArea	0.8201716840253008	0.8201716840253008	0.00	✓
portViolations	0	0	0.00	✓