feat(tests): Add comprehensive tests for SSR admin vendors module

Add 8 BDD-style tests for the vendors module covering grid/list
operations and vendor merge functionality. Tests follow established
patterns from accounts_test.clj and include proper database
verification.

Tests Implemented:
- vendor-grid-loads-with-empty-database
- vendor-fetch-ids-returns-correct-structure
- vendor-fetch-page-returns-vendors
- vendor-hydrate-results-works
- vendor-merge-transfers-references
- vendor-merge-same-vendor-rejected
- vendor-merge-invalid-vendor-handled
- vendor-hydration-includes-all-fields

Key Implementation Details:
- Uses setup-test-data helper with unique temp IDs
- Tests focus on public interface (fetch-page, merge-submit)
- Follows BDD Given/When/Then pattern
- All 8 tests passing (26 assertions)

Documentation:
- Created implementation plan in docs/plans/
- Documented solution patterns in docs/solutions/
- Created code review todos for future improvements

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

todos/009-pending-p2-standardize-temp-id-generation.md

@@ -0,0 +1,160 @@
+---
+status: pending
+priority: p2
+issue_id: "009"
+tags: [testing, patterns, consistency, vendors, datomic]
+dependencies: []
+---
+
+# Standardize Temp ID Generation Pattern in vendors_test.clj
+
+## Problem Statement
+
+The vendors test file uses **inconsistent** temp ID generation patterns:
+1. `(str "vendor-" (java.util.UUID/randomUUID))` in create-vendor helper
+2. `(str "vendor-" (rand-int 100000))` in test bodies
+3. `(str "vendor-source-" (rand-int 100000))` for merge tests
+
+This inconsistency:
+- Creates confusion about which pattern to use
+- `rand-int` has collision risk (1 in 100,000 per test)
+- Makes code harder to maintain
+
+## Findings
+
+**Inconsistent patterns identified by pattern-recognition-specialist:**
+
+**Line 22:**
+```clojure
+(defn create-vendor ...
+  {:db/id (str "vendor-" (java.util.UUID/randomUUID)) ...})
+```
+
+**Lines 74, 96, 123, 140, 161:**
+```clojure
+(let [vendor-temp-id (str "vendor-" (rand-int 100000)) ...])
+(let [source-temp-id (str "vendor-source-" (rand-int 100000)) ...])
+```
+
+**accounts_test.clj pattern:**
+Uses `(rand-int 100000)` consistently throughout.
+
+## Proposed Solutions
+
+### Option A: Standardize on UUID (Recommended)
+**Effort:** Small (10 minutes)
+**Risk:** Low
+
+Replace all `(rand-int 100000)` with `(java.util.UUID/randomUUID)`:
+```clojure
+;; Helper function
+(defn- generate-temp-id [prefix]
+  (str prefix "-" (java.util.UUID/randomUUID)))
+
+;; Usage
+(let [vendor-temp-id (generate-temp-id "vendor") ...]
+(let [source-temp-id (generate-temp-id "vendor-source") ...]
+```
+
+**Pros:**
+- Virtually zero collision probability
+- Consistent across all tests
+- UUID is standard for unique IDs
+
+**Cons:**
+- Slightly longer IDs (but doesn't matter for tests)
+- Different from accounts_test.clj pattern
+
+### Option B: Standardize on rand-int (Matching accounts_test.clj)
+**Effort:** Small (10 minutes)
+**Risk:** Low
+
+Change create-vendor to use rand-int:
+```clojure
+(defn create-vendor ...
+  {:db/id (str "vendor-" (rand-int 100000)) ...})
+```
+
+**Pros:**
+- Matches accounts_test.clj exactly
+- Shorter IDs
+- Simpler
+
+**Cons:**
+- Collision risk (though statistically low)
+- UUID is more standard for uniqueness
+
+### Option C: Use Sequential IDs
+**Effort:** Small (5 minutes)
+**Risk:** Low
+
+Use simple sequential pattern:
+```clojure
+;; No random generation needed
+(let [vendor-temp-id "vendor-hydrate-test" ...])
+```
+
+**Pros:**
+- Simplest possible
+- No collision risk
+- Self-documenting IDs
+
+**Cons:**
+- Different from accounts_test.clj
+- Tests may fail if run concurrently (same IDs)
+
+## Recommended Action
+
+**Go with Option A** - standardize on UUID:
+1. Create helper function for consistency
+2. Update all test temp IDs to use UUID
+3. Update create-vendor helper to use UUID
+
+This provides the safest pattern with zero collision risk.
+
+## Technical Details
+
+**Affected Lines:**
+- Line 22: create-vendor helper
+- Lines 74, 96, 97, 123, 140, 161: Test temp IDs
+
+**Implementation:**
+```clojure
+(defn- temp-id [prefix]
+  (str prefix "-" (java.util.UUID/randomUUID)))
+
+;; Replace all instances:
+(temp-id "vendor")           ; instead of (str "vendor-" (rand-int 100000))
+(temp-id "vendor-source")    ; instead of (str "vendor-source-" (rand-int 100000))
+(temp-id "vendor-target")    ; etc.
+```
+
+**Verification:**
+```bash
+lein test auto-ap.ssr.admin.vendors-test
+lein cljfmt check
+```
+
+## Acceptance Criteria
+
+- [ ] Helper function created for temp ID generation
+- [ ] All tests use consistent UUID-based temp IDs
+- [ ] create-vendor helper updated
+- [ ] Tests pass
+- [ ] Code formatted with lein cljfmt
+
+## Work Log
+
+### 2026-02-07 - Initial Creation
+
+**By:** Pattern Recognition Specialist Agent
+
+**Actions:**
+- Identified inconsistent ID generation patterns
+- Documented all occurrences
+- Created todo for standardization
+
+**Learnings:**
+- accounts_test.clj uses rand-int consistently
+- UUID provides better collision resistance
+- Consistency across codebase is important for maintainability