feat(data-platform): add /data-gate command

Binary pass/fail gate command for projman orchestrator integration.

- Invoked when Domain/Data label present on issue
- Checks FAIL-level violations only (speed optimization)
- Returns compact PASS/FAIL output for automation
- Graceful degradation when database/dbt unavailable

Completes the Domain Advisory Pattern for data domain.

Closes #375

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plugins/data-platform/commands/data-gate.md

@@ -0,0 +1,104 @@
+---
+description: Data integrity compliance gate (pass/fail) for sprint execution
+arguments:
+  - name: path
+    description: File or directory to validate
+    required: true
+---
+
+# /data-gate
+
+Binary pass/fail validation for data integrity compliance. Used by projman orchestrator during sprint execution to gate issue completion.
+
+## Usage
+
+```
+/data-gate <path>
+```
+
+**Examples:**
+```
+/data-gate ./dbt/models/staging/
+/data-gate ./portfolio_app/toronto/parsers/
+/data-gate ./dbt/
+```
+
+## What It Does
+
+1. **Activates** the `data-advisor` agent in gate mode
+2. **Loads** the `skills/data-integrity-audit.md` skill
+3. **Determines scope** from target path:
+   - dbt project directory: full dbt validation (parse, compile, test, lineage)
+   - Python files with database operations: schema validation
+   - SQL files: dbt model validation
+   - Mixed: all applicable checks
+4. **Checks only FAIL-level violations:**
+   - dbt parse failures (project broken)
+   - dbt compilation errors (SQL invalid)
+   - Missing tables/columns referenced in code
+   - Data type mismatches that cause runtime errors
+   - Broken lineage (orphaned model references)
+   - PostGIS SRID mismatches
+5. **Returns binary result:**
+   - `PASS` - No blocking violations found
+   - `FAIL` - One or more blocking violations
+
+## Output
+
+### On PASS
+```
+DATA GATE: PASS
+No blocking data integrity violations found.
+```
+
+### On FAIL
+```
+DATA GATE: FAIL
+
+Blocking Issues (2):
+1. dbt/models/staging/stg_census.sql - Compilation error: column 'census_yr' not found
+   Fix: Column was renamed to 'census_year' in source table. Update model.
+
+2. portfolio_app/toronto/loaders/census.py:67 - References table 'census_raw' which does not exist
+   Fix: Table was renamed to 'census_demographics' in migration 003.
+
+Run /data-review for full audit report.
+```
+
+## Integration with projman
+
+This command is automatically invoked by the projman orchestrator when:
+
+1. An issue has the `Domain/Data` label
+2. The orchestrator is about to mark the issue as complete
+3. The orchestrator passes the path of changed files
+
+**Gate behavior:**
+- PASS: Issue can be marked complete
+- FAIL: Issue stays open, blocker comment added with failure details
+
+## Differences from /data-review
+
+| Aspect | /data-gate | /data-review |
+|--------|------------|--------------|
+| Output | Binary PASS/FAIL | Detailed report with all severities |
+| Severity | FAIL only | FAIL + WARN + INFO |
+| Purpose | Automation gate | Human review |
+| Verbosity | Minimal | Comprehensive |
+| Speed | Skips INFO checks | Full scan |
+
+## When to Use
+
+- **Sprint execution**: Automatic quality gates via projman
+- **CI/CD pipelines**: Automated data integrity checks
+- **Quick validation**: Fast pass/fail without full report
+- **Pre-merge checks**: Verify data changes before integration
+
+For detailed findings including warnings and suggestions, use `/data-review` instead.
+
+## Requirements
+
+- data-platform MCP server must be running
+- For dbt checks: dbt project must be configured (auto-detected via `dbt_project.yml`)
+- For PostgreSQL checks: connection configured in `~/.config/claude/postgres.env`
+- If database or dbt unavailable: applicable checks skipped with warning (non-blocking degradation)