docs: add documentation impact to acceptance audit

[CleanDev-Fix]

Description

Extends the existing canonical acceptance-criteria completion table with a
Documentation Impact field. This keeps one audit system while making every
criterion identify affected documents or an explicit N/A with a reason.

Changed files:

• docs/traceability-mapping.md — adds the field, examples, definitions, and
  incomplete-criteria guidance;
• .github/PULL_REQUEST_TEMPLATE.md — collects documentation impact for every
  criterion;
• CONTRIBUTING.md — makes the field part of the required contributor flow;
• docs/evaluation-readiness.md — updates the central table example; and
• docs/pr-evidence-checklist.md — adds documentation impact to PR evidence
  and maintainer review guidance.

Related Issues

Fixes #143

Completion Table

Acceptance Criterion	Status	Implementation Evidence	Test Evidence	Documentation Impact
AC 1: Acceptance criteria audit template is added	Complete	Extended the existing canonical completion table in docs/traceability-mapping.md and .github/PULL_REQUEST_TEMPLATE.md; no duplicate template added	Markdown table consistency and content checks	docs/traceability-mapping.md, .github/PULL_REQUEST_TEMPLATE.md
AC 2: Template includes implementation evidence	Complete	Canonical table retains its required Implementation Evidence column	Content assertion	N/A — existing field retained
AC 3: Template includes test evidence	Complete	Canonical table retains its required Test Evidence column	Content assertion	N/A — existing field retained
AC 4: Template includes documentation impact	Complete	Added Documentation Impact to the guide, template, and central example, with explicit N/A guidance	Content and table checks	All five changed files align on the new field
AC 5: Incomplete criteria handling is explained	Complete	Expanded Handling Incomplete Criteria to record completed and deferred documentation	Content assertion	docs/traceability-mapping.md
AC 6: PR template or contributor docs reference the audit	Complete	Updated both the PR template and required completion-table step in CONTRIBUTING.md	Relative-link validation	.github/PULL_REQUEST_TEMPLATE.md, CONTRIBUTING.md, docs/pr-evidence-checklist.md

Detailed Traceability Mapping

Not applicable. This documentation/template-only patch does not change storage,
events, or security controls; the existing detailed table is preserved.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Chore

PR Evidence Checklist

1. Issue Reference

• This description links to and closes issue Add Aegis Contracts acceptance criteria audit template #143.

2. Implementation Summary

• Summary and changed-file responsibilities are listed above.
• No public functions, events, error codes, or roles are introduced.

3. Tests Added or Justification

• No executable tests were added because this patch changes Markdown and the
  PR template only; no contract or workflow behavior changes.

4. Commands Run

• git diff --check — PASS (line-ending warnings only; no whitespace errors)
• six acceptance-criteria content assertions — PASS
• Markdown table column/row consistency — PASS
• repository-relative Markdown link validation — PASS
• independent QA — PASS, no blocking or actionable findings

5. CI Status

This PR is intentionally a draft until relevant hosted checks are visible and
green.

6. Acceptance Criteria Coverage

• Every criterion is mapped in the Completion Table.
• Documentation impact is recorded for every criterion.
• No criterion is Partial or Not Met.

Contributor Self-Review

• Every acceptance criterion is addressed and mapped above.
• The patch stays within the issue scope and extends the current canonical
  table instead of adding a duplicate.
• No contract behavior, authorization, storage, events, error codes,
  dependencies, or workflow behavior changes.
• Relevant contributor, evaluation, evidence, and PR-template guidance is
  updated consistently.
• Focused documentation checks and independent QA pass.
• Hosted CI is pending; this PR remains a draft until relevant checks are
  visible and green.

Known limitation: the Rust/contract suite was not run because the patch changes
Markdown and the PR template only.

Additional Context

This patch deliberately extends the completion table introduced by #136 rather
than creating a competing audit template.

[El-swaggerito]

\nThis PR is currently a draft.\n\nThe auto-merge automation will not merge draft pull requests.