docs: integrate BDD lifecycle practice

[dapi]

What changed

• add a canonical Behavior Specification Practice for the BDD cycle Discovery → Formulation → Automation;
• integrate behavior discovery and scenario-quality gates into Feature Flow;
• add downstream behavior coverage and change-impact rules to Use Case Flow;
• extend feature brief, use-case, design, implementation-plan, and feature-local use-case templates;
• clarify BDD automation boundaries in testing policy;
• update priming manifests, indexes, artifact routing, and README navigation;
• cite Dan North's original Introducing BDD article as a methodology source.

Why

Memory Bank already separates project-level UC-*, feature acceptance SC-* / NEG-*, checks CHK-*, and test evidence, but did not define how BDD should operate across those owners. Without an explicit contract, downstream projects can duplicate requirements in Gherkin, treat BDD as an E2E framework, or create a parallel scenario hierarchy.

This change keeps one ownership chain:

UC → BR/REQ → SC/NEG → CHK → automated test → EVID

BDD remains a practice inside the selected delivery flow, not a new Task Routing branch or a memory-bank/bdd/ catalog.

Impact

• behavior-heavy features discover rules, examples, questions, and deferred scope before Problem Ready;
• structured examples use domain language and observable context/event/outcome;
• plans map required scenarios to the lowest reliable test surface rather than defaulting to E2E;
• use cases remain canonical for stable project behavior while feature briefs retain acceptance ownership.

Validation

• ruby tools/validate-priming-manifests.rb template/memory-bank
• memory-bank-cli lint --scope-root template/memory-bank --entrypoint template/memory-bank/README.md
• memory-bank-cli doctor --profile template
• git diff --check

Closes #113

[dapi]

Plan Ready artifact review — frozen draft candidate

Reviewed revision: c8791bd02e0bd62c34d2767783c2ae90ba139619

Reviewer: independent read-only requirements/artifact reviewer

Verdict: pass_with_notes

Blocking findings: 0 critical, 0 important.

Previous blockers are closed:

• the complete FT-113 candidate is frozen in one immutable revision;
• issue docs: integrate BDD into use-case and feature lifecycle #113 links to the commit, canonical brief, implementation plan, and PR.

Verified on the reviewed revision:

• issue requirements map to REQ-01..03 and SC-01..03;
• no new BDD route, identifier family, parallel owner, mandatory Gherkin/Cucumber/E2E, or bulk migration;
• frontmatter, lifecycle ownership, stable IDs, and REQ → SC → CHK → EVID traceability are consistent;
• priming manifest test and validator pass;
• template lint passes;
• template doctor reports 0 errors and 0 warnings;
• git diff --check origin/main...c8791bd passes.

Non-blocking notes:

• PR merge state is currently DIRTY; this affects merge readiness, not artifact correctness.
• Per Feature Flow, the plan must now move from draft to active; that new frozen revision requires one final clean re-review before Plan Ready is closed.

[dapi]

Final Plan Ready artifact re-review — active plan

Reviewed revision: 4bbed5e90fa870e8afb7dce1aeb5e8b785d6dcbe

Reviewer: independent read-only requirements/artifact reviewer

Verdict: pass

• Critical findings: 0
• Important findings: 0
• Plan Ready: closed

Compared with the reviewed draft candidate c8791bd, only the intended lifecycle transition changed: plan draft → active, its lifecycle note/purpose, and the README annotation. brief.md is byte-identical; requirements, scope, stable IDs, test strategy, steps, checkpoints, and evidence contract did not drift.

Re-verified:

• git diff --check: pass
• priming-manifest unit test: pass
• 16 priming manifests validated
• template lint: pass
• template doctor: 0 errors, 0 warnings

Non-blocking: PR #114 remains draft and currently reports DIRTY. Execution/Done evidence is intentionally pending and brief.md remains delivery_status: planned.

[dapi]

Post-main-merge artifact review

Reviewed revision: 37eaf34beff23ddc12f76f53662163577bdf6042

Verdict: pass

• Critical findings: 0
• Important findings: 0
• Prior Plan Ready verdict remains valid.

FT-113 brief, active implementation plan, and canonical BDD governance are unchanged from the reviewed Plan Ready revision. The BDD/User Story/Use Case guide brought from current main is consistent with the same ownership contract and introduces no contradictory acceptance owner.

Local post-merge checks pass: manifest tests/validation, both template and project Memory Bank lint scopes, template doctor (0 errors/0 warnings), and git diff --check.

[dapi]

Delivered-diff and closure review

Merged revision reviewed: 48f67fa93ebfca40603b06e7f764751c61c2df43

Verdict: delivered documentation pass; current closure candidate fail

• Critical findings: 0
• Important findings: 1

The delivered diff satisfies REQ-01..03, preserves canonical ownership, is proportionate, and is not overengineered. PR/CI/review evidence is factual.

Blocking closure finding: FT-113 remained delivery_status: planned through the merged revision, so changing it directly to done would skip the mandatory Plan Ready → Execution transition. Required correction: first freeze a distinct in_progress revision with the plan active, then record done / archived in a subsequent revision.

This external record serves as the separate delivered-diff/documentation review; a final closure re-review remains required after the lifecycle correction.