fix: enforce policy priority minimum

[amavashev]

Summary

• reject negative policy priorities in create and changed edit requests, with matching native form constraints
• preserve unrelated edits on legacy negative-priority rows and provide explicitly associated repair guidance
• drive the legacy input constraint, aria-describedby, and guidance visibility from one computed predicate
• stop empty stored override objects from reopening Advanced options
• advance dashboard/spec documentation and pins to v0.1.25.85 / governance 0.1.25.42
• pin the shipped Compose fleet to the published admin server v0.1.25.55 image

Validation

• 1,514/1,514 tests across 128 files
• 98.21% line coverage
• strict typecheck
• ESLint
• production build (BaseChart remains a separate lazy chunk)
• deployment-pin tests
• npm audit: 0 vulnerabilities
• git diff --check

Dependencies

• fix(governance): require non-negative policy priority cycles-protocol#141 at 402307a88906e9fd090159e5ccf2d0036e6aec83
• fix: enforce non-negative policy priority cycles-server-admin#224 at 9f633159ab1724f870b502c1dff16f8769b44fae
• runcycles/cycles-server-admin v0.1.25.55 published from main commit 83f708abe4e793c50d257d53db0bde2100c0a444

The admin v0.1.25.55 release passed its vulnerability gate and published-image readiness, version, and 401-shape smoke probes. Its immutable and latest tags both resolve to sha256:c1091aab55ecd9ab40fa39cc6e77ddf5d59102611fce099929abf2c91e468dc2.