docs: add Contributing section and changelog entry for contributors ladder

[mrizzi]

Summary

• Add a Contributing section to README.md referencing CONTRIBUTING.md for contributor guidance
• Add an [Unreleased] changelog entry for the contributors ladder infrastructure (CONTRIBUTING.md, CODEOWNERS, GitHub Issue templates)

Implements TC-5082

Summary by Sourcery

Document contributor guidance and record the new contributors ladder infrastructure in the changelog.

Documentation:

• Add a Contributing section in the README pointing to CONTRIBUTING.md for contributor guidance, promotion criteria, and workflows.

Chores:

• Add an Unreleased changelog entry describing the contributors ladder infrastructure including CONTRIBUTING.md, CODEOWNERS, and GitHub issue templates.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adds contributor guidance documentation by introducing a Contributing section in the README that points to CONTRIBUTING.md and documenting the new contributors ladder infrastructure in the Unreleased section of the changelog.

File-Level Changes

Change	Details	Files
Document contributors ladder infrastructure in changelog under an Unreleased section.	Introduce a new 'Unreleased' section at the top of the changelog. Add an 'Added' subsection describing the contributors ladder and related infrastructure (CONTRIBUTING.md, CODEOWNERS, GitHub Issue templates) and referencing the tracking ticket.	CHANGELOG.md
Expose contributor guidance and workflows from the main README.	Add a 'Contributing' section near the end of the README. Link to CONTRIBUTING.md and briefly describe that it contains the contributors ladder, promotion criteria, and issue/PR workflows.	README.md

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[sourcery-ai]

Hey - I've found 1 issue, and left some high level feedback:

• The changelog entry references TC-5072 while the PR description references TC-5082; align these ticket IDs so the changelog and PR point to the same tracker item.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The changelog entry references TC-5072 while the PR description references TC-5082; align these ticket IDs so the changelog and PR point to the same tracker item.

## Individual Comments

### Comment 1
<location path="CHANGELOG.md" line_range="12" />
<code_context>
+
+### Added
+
+- Contributors ladder with CONTRIBUTING.md, CODEOWNERS, and GitHub Issue templates (TC-5072)
+
 ## [0.12.2] - 2026-07-03
</code_context>
<issue_to_address>
**suggestion (typo):** Consider changing "Contributors ladder" to "contributor ladder" for more natural grammar.

"Contributors ladder" is uncommon; "contributor ladder" is the standard phrasing in documentation about contribution levels.

```suggestion
- Contributor ladder with CONTRIBUTING.md, CODEOWNERS, and GitHub Issue templates (TC-5072)
```
</issue_to_address>

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[mrizzi]

[sdlc-workflow/verify-pr] Re: @sourcery-ai[bot] review — Classified as suggestion — the changelog entry references TC-5072 (the Feature issue encompassing the entire contributors ladder initiative), while the PR references TC-5082 (the specific implementation Task). These are intentionally different Jira entities at different hierarchy levels. No sub-task created.

[mrizzi]

Verification Report for TC-5082 (commit 402e544)

Check	Result	Details
Review Feedback	PASS	2 items classified (1 nit, 1 suggestion); no code change requests
Root-Cause Investigation	N/A	No sub-tasks created — nothing to investigate
Scope Containment	PASS	PR modifies exactly CHANGELOG.md and README.md — matches task spec
Diff Size	PASS	12 lines added across 2 files — proportionate for docs-only task
Commit Traceability	PASS	Commit 402e544 references "Implements TC-5082"
Sensitive Patterns	PASS	No secrets or credentials in diff
CI Status	PASS	All 3 checks pass (Plugin Validation, Skill Lint, Sourcery)
Acceptance Criteria	PASS	4 of 4 criteria met
Test Quality	N/A	No test files in PR; Eval Quality: N/A
Test Change Classification	N/A	No test files in PR
Verification Commands	N/A	No verification commands specified

Overall: PASS

All checks pass. The PR adds a Contributing section to README.md referencing CONTRIBUTING.md and an [Unreleased] changelog entry for the contributors ladder infrastructure. Review feedback from sourcery-ai[bot] was classified as non-blocking (1 nit, 1 suggestion).

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This comment was AI-generated by sdlc-workflow/verify-pr v0.12.2.