Upgrade to Sphinx-Needs 8.x and classify new schema/link features

[patdhlk]

Summary

• Upgrade sphinx-needs to 8.x (>=8.0.0,<9) and migrate ubproject.toml off the deprecated SN 6.x config forms (extra_options list → [needs.fields.*], [[needs.extra_links]] → [needs.links.*], [needs.global_options.style] → [needs.fields.style]).
• Extend the safety classification with the new SN 8.x capabilities: JSON-Schema-based schema validation, typed fields, typed link schemas, conditional links (NeedLink/parse_conditions), and link-condition export via needs_json_include_link_conditions.
• Extend the ubc classification with the new CLI features relevant to ISO 26262 tool qualification: ubc schema validate, ubc diff git, ubc agent-skill.

Toolchain changes

File	Change
pyproject.toml	sphinx-needs[plotting]>=8.0.0,<9, sphinx[test]>=8.2.3,<10
uv.lock	Resolved SN 8.0.0, jsonschema-rs, minijinja
ubproject.toml	14 [needs.fields.*], 13 [needs.links.*]; safety-enums on ti / si / td / tcl
tools/sphinx-needs/main.rst	TOOL_SN version → 8.0.0

New classification items (13)

Features (tools/sphinx-needs + tools/ubc)

• FE_SN_SCHEMA_VALIDATION — declarative needs_schema_definitions (local + network rules, violation severity).
• FE_SN_TYPED_FIELDS — typed [needs.fields.*] with JSON-Schema constraints.
• FE_SN_TYPED_LINK_SCHEMA — cardinality (minItems / maxItems) on [needs.links.*].
• FE_SN_LINK_CONDITIONS — SN 8.0 NeedLink / parse_conditions.
• FE_SN_JSON_LINK_CONDITIONS — SN 8.0 needs_json_include_link_conditions.
• FE_UBC_SCHEMA_VALIDATE — ubc schema validate CI gate.
• FE_UBC_DIFF_GIT — ubc diff git change-impact analysis.
• FE_UBC_AGENT_SKILL — ubc agent-skill ontology export for LLM tooling.

Each new feature carries 3–6 nested faults covering the safety-relevant failure modes (silent skip, wrong severity, missing coverage, drift, etc.).

Restrictions avoiding the new faults

• RE_SN_USE_SCHEMA (legacy needs_constraints is disallowed)
• RE_SN_SCHEMA_VIOLATION (severity = \"violation\" for safety invariants)
• RE_SN_TYPE_FIELDS (explicit schema.type on every field)
• RE_SN_LINK_CARDINALITY (schema.minItems on raises/avoids/checks/errors/responsible)
• RE_SN_JSON_LINK_COND (keep needs_json_include_link_conditions at default True)

Updated examples of FE_SPHINX_NEEDS_CUSTOMIZABLE_OPTIONS / _LINKS to the TOML form and marked FE_SPHINX_NEEDS_DYNAMIC_CONSTRAINTS as legacy with a cross-reference.

Verification

• uv sync installs sphinx-needs==8.0.0.
• sphinx-build -W -a -E -b html succeeds clean (0 warnings).
• Exported needs.json contains 284 needs (was 271); spot-check confirmed all 13 new IDs are present.

Test plan

• Reviewer pulls branch, runs uv sync && sphinx-build -W -a -E -b html . _build/html locally and confirms a clean build.
• Spot-check the new features / faults / restrictions render correctly in _build/html/tools/sphinx-needs/features.html, .../restrictions.html, _build/html/tools/ubc/features.html.
• Confirm the needflow / needtable on analysis/index and tools/sphinx-needs/main still render.
• Confirm the migrated link / field tables in ubproject.toml still drive the visible meta-data in existing needs (e.g. style predicates still color-code types).

Follow-ups (not in this PR)

• Author an actual schemas.json with ISO 26262 safety rules and wire it via schema_definitions_from_json.
• Add [scripts] entries for ubc schema validate / ubc build needs / ubc agent-skill.
• Classify more of the recent ubCode (VS Code extension) features under TOOL_UBCODE, which is currently a stub.