AUR-471 -- ISO/IEC 25010 weights and team convention are explicit configuration

Outcome

The eight ISO/IEC 25010 product quality characteristics now carry weights the team declares in a versioned file, .aurumcode/iso25010-weights.yml, and the review reports a per-characteristic score plus an aggregate coherent with those weights. The team may also declare its own convention: a per-characteristic severity limit and which characteristics are blocking versus informative.

Authority model

There are two kinds of input and they are not interchangeable:

Explicit user configuration. .aurumcode/iso25010-weights.yml is written and versioned by the team. It has authority over the review's severity policy, because the team is the principal and the file is its declaration.
Untrusted context. Repository prompt text, skills, MCP results, RAG chunks and any other provider-contributed material are DATA. They inform the reviewer and can never change a rule, a severity, the --fail-on gate, secret redaction, or a cost ceiling.

internal/config/policy reads, parses and validates the policy file and nothing else. It has no code path that consumes provider or prompt text, so the distinction is structural, not a runtime check.

The boundary explicit configuration still cannot cross

Authority over severity does not extend to switching off the deterministic security pass or secret redaction. A policy that tries to disable either is refused at load time with a named error that quotes the refused clause:

security_pass: false, security: false, security.pass: false
redaction: off, redact_secrets: false, security.redact_secrets: false

YAML aliases are dereferenced before the check, so an anchored spelling off: &off false plus redaction: *off is refused the same way, naming redaction; the indirection is not a bypass.

The Policy type has no field through which redaction or the security pass could be disabled, so the refusal holds even if a caller ignored the error.

File schema

weights:            # required; the eight ISO/IEC 25010 characteristics
  functionality: 0.15
  reliability: 0.15
  usability: 0.10
  efficiency: 0.12
  maintainability: 0.18
  portability: 0.08
  security: 0.17
  compatibility: 0.05   # must sum to 1.0 (tolerance 1e-9)

convention:         # optional
  severity_limit:
    security: error
    portability: info
  blocking: [security, reliability]
  informative: [portability]

Historical sections such as thresholds and static_signals are ignored for forward compatibility; a file that carries them still loads.

Named errors

All failures are errors.Is-able and print a stable code:

Error	Trigger
`policy: weights-sum`	weights missing or not summing to 1.0
`policy: invalid-weight`	a weight value cannot be decoded as a number
`policy: non-finite-weight`	a weight is `NaN` or infinite (e.g. `.nan`)
`policy: negative-weight`	a weight is negative
`policy: unknown-characteristic`	a name outside ISO/IEC 25010
`policy: invalid-severity`	a limit outside `error`/`warning`/`info`
`policy: blocking-informative-overlap`	a characteristic is both
`policy: refused-clause`	policy tries to disable security pass or redaction

The weights and refusal checks run inside Load, before any caller could reach the model, so an invalid declaration can never produce a model call.

Zero-configuration contract

A missing file is not an error and not an empty policy. Load returns (nil, nil), Evaluate returns (nil, nil), and Render emits exactly json.Marshal(result). A repository that has not declared weights gets today's output, byte for byte.

Scoring

For each characteristic in the canonical ISO order, contribution = score * weight; the aggregate is round(sum(contribution)). The report is coherent with the file by construction, so two declarations that move weight between characteristics produce different aggregates.

Validation

Unit: tests/unit/AUR-471.go::TestAUR471
Integration: tests/integration/AUR-471.go::IntegrationAUR471
Acceptance: tests/acceptance/AUR-471.sh (all, AC-001..AC-004)
E2E: tests/e2e/AUR-471.sh::E2EAUR471

Skeptical mutations AC-002-MUT-001 (silently normalize a non-1.0 sum) and AC-004-MUT-002 (let the policy disable redaction) each make the acceptance RED and restore GREEN on the unmutated package.