refactor(conflict-engine): extract shared doc-conflict-engine reference

Move the BLOCKER/WARNING/INFO conflict report format, severity semantics,
and safety-gate behavior from workflows/import.md into a new shared
reference file. /gsd-import consumes the reference; behavior is unchanged
(all 13 import-command tests + full 4091-test suite pass).

Prepares for /gsd-ingest-docs (#2387) which will consume the same contract
with its own domain-specific check list. Prevents drift between the two
implementations.

Refs #2387

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

commands/gsd/import.md

@@ -25,6 +25,7 @@ Future: `--prd` mode for PRD extraction is planned for a follow-up PR.
 @~/.claude/get-shit-done/workflows/import.md
 @~/.claude/get-shit-done/references/ui-brand.md
 @~/.claude/get-shit-done/references/gate-prompts.md
+@~/.claude/get-shit-done/references/doc-conflict-engine.md
 </execution_context>
 
 <context>

get-shit-done/references/doc-conflict-engine.md

@@ -0,0 +1,91 @@
+# Doc Conflict Engine
+
+Shared conflict-detection contract for workflows that ingest external content into `.planning/` (e.g., `/gsd-import`, `/gsd-ingest-docs`). Defines the report format, severity semantics, and safety-gate behavior. The specific checks that populate each severity bucket are workflow-specific and defined by the calling workflow.
+
+---
+
+## Severity Semantics
+
+- **[BLOCKER]** — Unsafe to proceed. The workflow MUST exit without writing any destination files. Used for contradictions of locked decisions, missing prerequisites, and impossible targets.
+- **[WARNING]** — Ambiguous or partially overlapping. The workflow MUST surface the warning and obtain explicit user approval before writing. Never auto-approve.
+- **[INFO]** — Informational only. No gate; no user prompt required. Included in the report for transparency.
+
+---
+
+## Report Format
+
+Plain-text, never markdown tables (no `|---|`). The report is rendered to the user verbatim.
+
+```
+## Conflict Detection Report
+
+### BLOCKERS ({N})
+
+[BLOCKER] {Short title}
+  Found: {what the incoming content says}
+  Expected: {what existing project context requires}
+  → {Specific action to resolve}
+
+### WARNINGS ({N})
+
+[WARNING] {Short title}
+  Found: {what was detected}
+  Impact: {what could go wrong}
+  → {Suggested action}
+
+### INFO ({N})
+
+[INFO] {Short title}
+  Note: {relevant information}
+```
+
+Every entry requires `Found:` plus one of `Expected:`/`Impact:`/`Note:` plus (for BLOCKER/WARNING) a `→` remediation line.
+
+---
+
+## Safety Gate
+
+**If any [BLOCKER] exists:**
+
+Display:
+```
+GSD > BLOCKED: {N} blockers must be resolved before {operation} can proceed.
+```
+
+Exit WITHOUT writing any destination files. The gate must hold regardless of WARNING/INFO counts.
+
+**If only WARNINGS and/or INFO (no blockers):**
+
+Render the full report, then prompt for approval via the `approve-revise-abort` or `yes-no` pattern from `references/gate-prompts.md`. Respect text mode (see the workflow's own text-mode handling). If the user aborts, exit cleanly with a cancellation message.
+
+**If the report is empty (no entries in any bucket):**
+
+Proceed silently or display `GSD > No conflicts detected.` Either is acceptable; workflows choose based on verbosity context.
+
+---
+
+## Workflow Responsibilities
+
+Each workflow that consumes this contract must define:
+
+1. **Its own check list per bucket** — which conditions are BLOCKER vs WARNING vs INFO. These are domain-specific (plan ingestion checks are not doc ingestion checks).
+2. **The loaded context** — what it reads (ROADMAP.md, PROJECT.md, REQUIREMENTS.md, CONTEXT.md, intel files) before running checks.
+3. **The operation noun** — substituted into the BLOCKED banner (`import`, `ingest`, etc.).
+
+The workflow MUST NOT:
+
+- Introduce new severity levels beyond BLOCKER/WARNING/INFO
+- Render the report as a markdown table
+- Write any destination file when BLOCKERs exist
+- Auto-approve past WARNINGs without user input
+
+---
+
+## Anti-Patterns
+
+Do NOT:
+
+- Use markdown tables (`|---|`) in the conflict report — use plain-text labels as shown above
+- Bypass the safety gate when BLOCKERs exist — no exceptions for "minor" blockers
+- Fold WARNINGs into INFO to skip the approval prompt — if user input is needed, it is a WARNING
+- Re-invent severity labels per workflow — the three-level taxonomy is fixed

get-shit-done/workflows/import.md

@@ -107,7 +107,7 @@ Extract from the imported content:
 
 <step name="plan_conflict_detection">
 
-Run conflict checks against the loaded project context. Output as a plain-text conflict report using [BLOCKER], [WARNING], and [INFO] labels. Do NOT use markdown tables (no `|---|` format).
+Run conflict checks against the loaded project context. The report format, severity semantics, and safety-gate behavior are defined by `references/doc-conflict-engine.md` — read it and apply it here. Operation noun: `import`.
 
 ### BLOCKER checks (any one prevents import):
 
@@ -128,45 +128,15 @@ Run conflict checks against the loaded project context. Output as a plain-text c
 - Plan uses a library not currently in the project tech stack → [INFO]
 - Plan adds a new phase to the ROADMAP.md structure → [INFO]
 
-Display the full Conflict Detection Report:
+Render the full Conflict Detection Report using the format in `references/doc-conflict-engine.md`.
 
-```
-## Conflict Detection Report
-
-### BLOCKERS ({N})
-
-[BLOCKER] {Short title}
-  Found: {what the imported plan says}
-  Expected: {what project context requires}
-  → {Specific action to resolve}
-
-### WARNINGS ({N})
-
-[WARNING] {Short title}
-  Found: {what was detected}
-  Impact: {what could go wrong}
-  → {Suggested action}
-
-### INFO ({N})
-
-[INFO] {Short title}
-  Note: {relevant information}
-```
-
-**If any [BLOCKER] exists:**
-
-Display:
-```
-GSD > BLOCKED: {N} blockers must be resolved before import can proceed.
-```
-
-Exit WITHOUT writing any files. This is the safety gate — no PLAN.md is written when blockers exist.
+**If any [BLOCKER] exists:** apply the safety gate from the reference — exit WITHOUT writing any files. No PLAN.md is written when blockers exist.
 
 **If only WARNINGS and/or INFO (no blockers):**
 
-
 **Text mode (`workflow.text_mode: true` in config or `--text` flag):** Set `TEXT_MODE=true` if `--text` is present in `$ARGUMENTS` OR `text_mode` from init JSON is `true`. When TEXT_MODE is active, replace every `AskUserQuestion` call with a plain-text numbered list and ask the user to type their choice number. This is required for non-Claude runtimes (OpenAI Codex, Gemini CLI, etc.) where `AskUserQuestion` is not available.
-Ask via AskUserQuestion using the approve-revise-abort pattern:
+
+Ask via AskUserQuestion using the approve-revise-abort pattern (see `references/gate-prompts.md`):
 - question: "Review the warnings above. Proceed with import?"
 - header: "Approve?"
 - options: Approve | Abort
@@ -267,7 +237,7 @@ Show: plan filename written, phase directory, validation result, next steps.
 ## Anti-Patterns
 
 Do NOT:
-- Use markdown tables (`|---|`) in the conflict detection report — use plain-text [BLOCKER]/[WARNING]/[INFO] labels
+- Violate the shared conflict-engine contract in `references/doc-conflict-engine.md` (no markdown tables, no new severity labels, no bypass of the BLOCKER gate)
 - Write PLAN.md files as `PLAN-01.md` or `plan-01.md` — always use `{NN}-{MM}-PLAN.md`
 - Use `pbr:plan-checker` or `pbr:planner` — use `gsd-plan-checker` and `gsd-planner`
 - Write `.planning/.active-skill` — this is a PBR pattern with no GSD equivalent