chore: add coverage reporting to make test

Update `make test` to show per-package coverage summary by default.
This makes coverage visible during normal development without requiring
a separate command.

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

Author: josealekhine

.context/TASKS.md

@@ -50,7 +50,7 @@
   - [x] `ctx session save` creates session file
   - [x] `ctx agent` returns context packet
 - [x] Set unit test coverage target (70% for internal/cli, internal/context)
-- [ ] Add coverage reporting to `make test`
+- [x] Add coverage reporting to `make test`
 - [ ] Add smoke test to CI/Makefile: build binary, run basic commands
 - [ ] Verify built binary executes subcommands (not silently falling through to root help)
 

Makefile

@@ -15,9 +15,9 @@ all: build
 build:
 	CGO_ENABLED=0 go build -o $(OUTPUT) ./cmd/ctx
 
-## test: Run tests
+## test: Run tests with coverage summary
 test:
-	CGO_ENABLED=0 CTX_SKIP_PATH_CHECK=1 go test ./...
+	@CGO_ENABLED=0 CTX_SKIP_PATH_CHECK=1 go test -cover ./...
 
 ## test-v: Run tests with verbose output
 test-v: