fix(traceability): align optional and status table contracts

[kreneskyp]

Summary

• declare Coverage Status for the functional-coverage table while retaining Status for test summaries
• mark suite and inspection targets optional, matching the existing adoption contract
• strengthen tests so both declarations are explicit and current Quire stays silent for a non-adopting repository

Verification

• composed against quire-rs#383 and spec-artifacts-iso#32/Declare the Task track property (FR-005) #33: 89 passed, 1 expected xfail
• ruff passed; every Python file passed black --check (the aggregate black invocation stalled in this environment, so files were checked individually)
• Engineering Assurance composed coverage: 45/46 backed; no status lies, undeclared statuses, unbacked references, status-column diagnostics, or optional evidence-target diagnostics

Dependencies

• fix(coverage): honor per-reference and optional targets quire-rs#383
• feat(schema): admit current trace-target selectors and postures spec-artifacts-iso#32
• feat(schema): support per-reference status columns spec-artifacts-iso#33

Keep draft until those dependencies merge and released pins are updated.