feat: requirements companion file, AGENTS.md hook, v3.1.0

* feat: add Requirements as default required section (#81)

Add a Requirements section (user stories + acceptance criteria) as the 8th
default required section, positioned after Purpose and before Public API.
This enables a natural product/AI workflow where humans define what a module
should do from a user perspective, and AI fills in the technical details.

- Add "Requirements" to default_required_sections() in types.rs
- Add ## Requirements to all 6 built-in language templates in generator.rs
- Update all 15 project spec files with the new section
- Update docs, config, and all test fixtures
- Bump version to 3.1.0

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* docs: update README and docs for Requirements section (v3.1.0)

Add Requirements to all default section lists, config examples, spec
examples, and AGENTS.md. Add v3.1.0 CHANGELOG entry.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* feat: move Requirements from required spec section to companion file

Requirements as a required spec section (v3.1.0) blurred the authorship
boundary between technical contracts and product asks. This moves
requirements to a per-module companion file (requirements.md) alongside
tasks.md and context.md, keeping specs focused as dev-authored technical
contracts while giving Product/Design their own space.

Changes:
- Remove "Requirements" from default required sections
- Remove ## Requirements from all spec templates (default + 5 languages)
- Add requirements.md companion file template with User Stories,
  Acceptance Criteria, Constraints, and Out of Scope sections
- Scaffold requirements.md alongside tasks.md and context.md
- Update all 15 existing specs and add requirements.md for each module
- Update docs, README, SCOPE, CLI docs, and integration tests

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* docs: update docs to reflect Requirements as companion file, bump to v3.2.0

Remove Requirements from required sections lists, config examples, and
minimal spec examples across all docs. Bump version from 3.1.0 to 3.2.0
and add changelog release link.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: version should be 3.1.0, not 3.2.0 — this is the first release since 3.0.0

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: clean up CHANGELOG — merge duplicate 3.1.0 entries, add AGENTS.md feature

The changelog had two conflicting [3.1.0] entries: one adding Requirements
as a required section, another moving it to companion file. Since v3.1.0
was never released, consolidate into a single clean entry. Also documents
the AGENTS.md hook target which was missing from the changelog.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* feat: populate all 15 requirements companion files with real content

Every requirements.md now contains grounded user stories, acceptance
criteria, constraints, and out-of-scope items derived from actual
module behavior. All 15 specs validated — 0 warnings, 0 failures,
100% coverage, avg score 99.8/100.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

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Co-authored-by: Claude Opus 4.6 <[email protected]>

Author: corvid-agent