docs: record Issue #16 User-Agent implementation learnings

- Added TypeScriptDev learning: USER_AGENT constant in src/lib/user-agent.ts,
  header set in ApimClient.request() at line 108
- Added TestEngineer learning: User-Agent testing patterns for both auth paths
- Closes #16

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: petehauge <12090616+petehauge@users.noreply.github.com>

Author: Copilot

.squad/agents/testengineer/history.md

@@ -79,4 +79,34 @@
 
 **Result:** 42 total tests in resource-uri.test.ts (32 existing + 13 new for buildResourceLabel, minus 3 restructured). All tests pass. Function behavior validated for all documented use cases.
 
+### 2026-04-29: User-Agent Header Testing (Issue #16)
+
+**Context:** Added test coverage for User-Agent header implementation across both lib and client layers.
+
+**Tests Created:**
+- `tests/unit/lib/user-agent.test.ts` - 3 tests
+  - ✅ USER_AGENT constant exports as string
+  - ✅ USER_AGENT matches format `apiops-cli/{version}`
+  - ✅ Version in USER_AGENT matches package.json version
+
+- `tests/unit/clients/apim-client.test.ts` - 2 new tests added to "User-Agent" describe block
+  - ✅ User-Agent header set on authenticated requests (Bearer token path)
+  - ✅ User-Agent header set on unauthenticated requests (skipAuth blob path)
+
+**Testing Approach:**
+- Verified header presence in both auth paths using standard mock setup
+- Both tests confirm header is set after auth logic via `headers.set()`
+- Used existing test patterns: mock fetch with Response objects, inspect headers in captured context
+
+**Code Review Feedback:**
+- One finding: duplicate test replaced with skipAuth blob path test to avoid redundancy
+- Ensures both auth flows are covered without test duplication
+
+**Pattern:** When testing client-wide headers:
+- Add lib unit test for constant/value verification
+- Add client integration tests for both supported request patterns
+- Verify header appears in expected request headers captured by mocks
+
+**Result:** 5 new User-Agent tests, all passing. Code review approved.
+
 <!-- Append new learnings here after each session -->

.squad/agents/typescriptdev/history.md

@@ -160,3 +160,30 @@ vi.mocked(fs.access).mockImplementation(async (p) => {
 Same rule applies to `expect(fs.copyFile).toHaveBeenCalledWith(...)` assertions — use the resolved form.
 
 **Files:** `tests/unit/services/init-service.test.ts`.
+
+### 2026-04-29: User-Agent Header Implementation (Issue #16)
+
+**Context:** Implemented User-Agent header for all APIM REST API calls to identify the apiops-cli client.
+
+**Key Decisions:**
+- Created `src/lib/user-agent.ts` with `USER_AGENT` constant using module pattern: `createRequire` loads package.json at module initialization
+- Format: `apiops-cli/{version}` (e.g., `apiops-cli/0.1.0`)
+- Header set in `ApimClient.request()` at line 108, after auth logic but before retry loop
+- Applied universally to all request types: authenticated (Bearer token) and unauthenticated (SAS blob skipAuth paths)
+
+**Pattern:** When exporting client identifiers:
+- Use ES module pattern with `createRequire(import.meta.url)` to load package.json at import time
+- No runtime file system calls or dynamic version reads
+- Export as constant string from dedicated lib module
+- Consumed by clients that need the value
+
+**Files Modified:**
+- `src/lib/user-agent.ts` - New file
+- `src/clients/apim-client.ts` - Added header set at line 108
+
+**Implementation Details:**
+- `headers.set('User-Agent', USER_AGENT)` executes after skipping auth headers but maintaining compatibility
+- Tested on both auth paths: standard Bearer token and skipAuth (SAS blob)
+- Issue #16 closed
+
+**Tests:** Created `tests/unit/lib/user-agent.test.ts` (3 tests) and added to `apim-client.test.ts` (2 tests)