feat: prune SDK to API-key surface, add stats/usage/metrics/events

Strip session-only routes (auth, me, teams, hosts, channels, admin,
audit-logs) from api/openapi.yaml via new scripts/prune_openapi.py,
which is wired into `make generate` and `make prune-spec`. Spec drops
from 4787 to 1717 lines; regenerated _generated.py drops from 906 to
415 lines with all obsolete models removed.

Add SDK methods on CapsulesResource / AsyncCapsulesResource for the
apiKey-usable routes that were previously unwrapped:
  - capsules.stats(range=...)         -> CapsuleStats
  - capsules.usage(from_=..., to=...) -> UsageResponse (accepts date)
  - capsules.metrics(id, range=...)   -> CapsuleMetrics

Add EventsResource / AsyncEventsResource exposing
WrennClient.events.stream() over /v1/events/stream (SSE). Parser
handles `:keepalive` comments and multi-line `data:` frames.

Re-export new models (CapsuleStats, CapsuleMetrics, MetricPoint,
UsageResponse, SSEEvent, Resource, Actor) from wrenn.models.

Drop email-validator runtime dep (no EmailStr remains). Bump version
to 0.3.0 (pyproject + __version__). Add pyyaml to dev deps and
types-PyYAML to the pre-commit mypy hook for the prune script.

Normalize docstrings on new methods/classes to Google style with
Example:: blocks where useful. Regenerate docs/reference.md.

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

Makefile

@@ -1,5 +1,5 @@
 # Makefile
-.PHONY: generate lint test check test-integration test-code-runner
+.PHONY: generate gen-docs lint test check test-integration test-code-runner prune-spec
 
 # Variables
 SPEC_URL = "https://raw.githubusercontent.com/wrennhq/wrenn/refs/heads/main/internal/api/openapi.yaml"
@@ -12,6 +12,8 @@ generate:
 
 	curl -fsSL $(SPEC_URL) -o $(SPEC_PATH)
 
+	$(MAKE) prune-spec
+
 	uv run datamodel-codegen \
 		--input $(SPEC_PATH) \
 		--output src/wrenn/models/_generated.py \
@@ -40,6 +42,10 @@ test-code-runner:
 
 check: lint test
 
+prune-spec:
+	@echo "Pruning spec down to the SDK's API-key surface..."
+	uv run python scripts/prune_openapi.py $(SPEC_PATH)
+
 gen-docs:
 	mkdir -p docs
 	uv run pydoc-markdown > docs/reference.md