feat(hive-claude): add InfiniteSession (name+store+compaction policy)

hive-claude/README.md

@@ -15,19 +15,31 @@ on it rather than shelling out to `claude` by hand.
 
 ## Shape
 
-- **`Claude::run(&config, &session, prompt, &sink)`** → `Result<(), Error>`. A
-  clean turn is `Ok(())`; every non-completion state is an [`Error`] variant, so
-  you branch with a single `match`.
-- **`Claude::run_resume_or_create(&config, title, prompt, &sink)`** →
-  `Result<bool>`. Resumes a titled session, creating it on first use.
-  `Ok(true)` means a fresh session was minted.
+Two layers — reach for the high-level one:
+
+- **`InfiniteSession { name, store, policy }`** — a durable session that keeps
+  itself alive across the context window. `.run(&config, prompt, &sink)` →
+  `Result<Progress, Error>` does resume-or-create, compacts **reactively** on
+  overflow (compact + retry once), and **proactively** after a clean turn when
+  the policy says so (optional checkpoint turn, then compact). `.compact(…)`
+  forces one. `Progress { created, compacted }` reports what happened.
+- **`Claude::run(&config, &attach, prompt, &sink)`** → `Result<(), Error>` —
+  the low-level driver: one turn, one `Attach` target (`Resume` / `Create` /
+  `Continue` / `OneOff`). A clean turn is `Ok(())`; every other state is an
+  `Error` variant.
+
+Supporting pieces:
+
+- **`CompactionPolicy`** — decides *when* to compact. **`PercentPolicy`**
+  (`percent`, `default_window`, `checkpoint_prompt`) compacts at a percent of
+  the model window; **`NeverCompact`** never does.
 - **`Config`** — the invocation (model, effort, cwd, prompt/MCP files, tools,
-  extra args). **`Session`** — which session to attach to (`Resume` / `Create`
-  / `Continue` / `OneOff`).
-- **`Sink`** — a trait with no-op defaults; implement the methods you care
-  about to observe stream events, non-JSON stdout, and stderr. Use `NoopSink`
-  when you only want the result.
+  extra args).
+- **`Sink`** — a trait with no-op defaults; implement what you care about to
+  observe stream events, non-JSON stdout, and stderr. `NoopSink` ignores all.
 - **`SessionStore`** — locate and archive on-disk sessions by title.
+- **`Usage`** — the minimal context signal (`context_tokens`,
+  `context_window`) the policy sees.
 
 `Error` unifies the two things that can stop a turn: recognized **sentinels**
 (`PromptTooLong`, `RateLimited`, `AuthFailed`, `SessionNotFound`) and **hard