docs: add discovery gap analysis model

TASKS.md

@@ -607,33 +607,64 @@ Definition of Done:
 - Guidance helps reduce token usage without preventing useful technical reasoning
 - Existing workflow remains unchanged
 
-## TASK-025 — Discovery gap analysis
+## TASK-025 — Define discovery gap analysis model
+
+Status: Done
+
+Role: Architecture Agent
+
+Goal:
+Define how missing or weak project context should be detected and converted into targeted follow-up discovery questions.
+
+Acceptance Criteria:
+
+- Define gap detection rules
+- Define gap severity levels
+- Define question generation rules
+- Define question prioritisation rules
+- Define mapping between missing context sections and follow-up questions
+- Document the model
+- Define the follow-on implementation task
+- No implementation
+
+Definition of Done:
+
+- Gap analysis model documented
+- Follow-up question model documented
+- Example gap-to-question mappings included
+- TASK-026 implementation task defined
+
+Result
+
+Created `context/gap-analysis-model.md` (320 lines) as a planning artifact documenting:
+
+1. **Gap detection rules** — 4 rule types (GAP-01 through GAP-04): TBD placeholders, unmapped sections, partial content, near-empty files
+2. **Severity levels** — S1 (Critical), S2 (Important), S3 (Low) with assignment criteria per stage and mapping status
+3. **Question generation rules** — 6 rules (QG-01 through QG-06): one-gap-per-question, answerable format, section reference, table-column specificity, skip-filled sections, owner-answer alignment
+4. **Question prioritisation** — Ordered by severity → file completeness → dependency order → question scope
+5. **Gap-to-question mapping table** — 40+ section-level mappings across all 16 template context files (excludes CLI-managed project-level files)
+6. **End-to-end example flow** — Step-by-step walkthrough from detection through prioritisation to follow-up generation to regeneration
+7. **Edge cases** — Partial sections, acceptable TBDs, new templates, multi-question sections, heading-only files
+8. **TASK-026 implementation scope** — CLI command spec (`rdb gap`), module structure, test requirements (~45 tests across 6 categories)
+
+## TASK-026 — Implement discovery gap analysis
 
 Status: Todo
 
 Role: Implementation Agent
 
 Goal:
-Identify missing context and generate targeted follow-up questions.
-
-Implementation Gap:
-Context health can identify missing information, but there is no automated way to generate follow-up discovery questions from those gaps.
+Implement the approved discovery gap analysis model.
 
 Acceptance Criteria:
 
 - Analyse generated context files
-- Detect empty sections
+- Detect missing sections
 - Generate follow-up questions
 - Link questions to missing context sections
 - Add/update tests
 
-Definition of Done:
-
-- Gap analysis command exists
-- Missing context produces targeted questions
-- Tests pass
-
-## TASK-026 — Context-driven follow-up questions
+## TASK-027 — Context-driven follow-up questions
 
 Status: Todo
 
@@ -658,7 +689,7 @@ Definition of Done:
 - Follow-up questions are linked to discovery answers
 - Tests pass
 
-## TASK-027 — Improve discovery answer reliability UX
+## TASK-028 — Improve discovery answer reliability UX
 
 Status: Todo
 
@@ -684,7 +715,7 @@ Definition of Done:
 - Mapping to internal confidence levels is defined
 - Future implementation work is clearly specified
 
-## TASK-028 — Capture AI tool targets
+## TASK-029 — Capture AI tool targets
 
 Status: Todo