clients/python: v0.2 multi-turn Session API

- Session class wrapping a clawdforge session_id; context-manager auto-close
- forge.session(agent=...) block form (preferred)
- forge.create_session() / forge.list_sessions() / forge.get_session() admin shapes
- TurnResult dataclass with .text() helper concatenating text events
- Idempotent Session.close() — safe in finally / __exit__
- tests/test_sessions.py: 16 tests covering block/manual/idempotency/exception/list/state/text-helper/v0.1-regression
- README "Multi-turn / Sessions (v0.2)" section
- pyproject version 0.1.0 -> 0.2.0; package __version__ matches

Architecture: matches the existing v0.1 client — sync, requests-based,
single Forge-owned requests.Session for connection pooling. Session holds
a back-reference to the Forge for HTTP work (no per-Session HTTP client).
This mirrors how Forge already exposes its own context-manager pattern, so
nothing about the threading/lifecycle story changes for callers.

v0.1 /run path unchanged — 49 existing tests still green, +16 new tests
for v0.2 (target was 9; covered the spec's 9 plus extras for empty-prompt
local validation, include_closed=false param, empty-id ValueError, and
s.state() round-trip).

mypy --strict src/clawdforge/ clean.

Spec: memory/spec-clawdforge-v0.2.md
Server core: 940861f

clients/python/pyproject.toml

@@ -4,8 +4,8 @@ build-backend = "hatchling.build"
 
 [project]
 name = "clawdforge"
-version = "0.1.0"
-description = "Python SDK for the clawdforge LAN-only HTTP service (claude -p subprocess wrapper)."
+version = "0.2.0"
+description = "Python SDK for the clawdforge LAN-only HTTP service — single-turn /run plus multi-turn /sessions (v0.2)."
 readme = "README.md"
 requires-python = ">=3.10"
 authors = [{ name = "Kayos", email = "kayos@sulkta.com" }]