docs: give turn-loop/ a README.md landing page

Part of hyperhive#1898 (b): every docs subdir should have a top-level
README.md link, achieved by moving/renaming where an existing file
already fits the role.

docs/turn-loop.md already served as the hub + index for the three
sub-pages under turn-loop/ (claude-invocation.md, config.md, mcp.md),
so it moves wholesale rather than leaving a redundant top-level
pointer stub. Fixes every inbound/relative link across the repo
(top-level README.md, CLAUDE.md, docs/persistence.md,
docs/tools/scheduling.md, the sub-pages own back-link, hive-agent
README + doc comments, hive-agent/Cargo.toml, .prettierignore per-file
exemption entry) - grepped the whole tree for both turn-loop.md and
turn-loop/ to find every reference rather than trusting a partial
list.

nix fmt clean, cargo check -p hive-agent clean.

docs/persistence.md

@@ -239,7 +239,7 @@ Survives destroy/recreate, gone on `--purge`.
 Empty marker file. Its presence parks the agent's turn loop: the
 harness keeps serving its web UI and MCP daemons but drives no turns,
 and inbox messages queue unacked until it's removed (see
-[turn loop](turn-loop.md#the-loop)).
+[turn loop](turn-loop/README.md#the-loop)).
 
 Unusually, it's read and written from **both** sides of the harness
 bind-mount, and that's the whole design: the harness stats it

docs/tools/scheduling.md

@@ -89,6 +89,6 @@ lifecycle events, or another container's boot log.
 ## See also
 
 - `remind` (no-approval self-wake path) — documented in
-  [`docs/turn-loop.md`](../turn-loop.md).
+  [`docs/turn-loop/`](../turn-loop/README.md).
 - [`docs/approvals.md`](../approvals.md) — approval flow for
   `request_schedule_prompt`.

docs/turn-loop/README.md

@@ -14,7 +14,7 @@ agents) runs:
    queued and unacked, so a resume drains the backlog instead of
    losing it; reminders and todo wakes buffer in their channels. Set
    it with `hivectl agent <name> pause` or the dashboard toggle; see
-   [persistence](persistence.md#-harnesspaused-per-agent).
+   [persistence](../persistence.md#-harnesspaused-per-agent).
 1. Long-poll `Recv` on its socket. The host-side broker
    (`broker.rs::recv_blocking_batch`) returns immediately if there's
    a pending message, otherwise waits up to 30 s for a broker `Sent`
@@ -31,7 +31,7 @@ agents) runs:
    hard failure. The outcome drives the post-turn action (see
    [Turn outcomes](#turn-outcomes)); compaction is handled inside the
    session (see
-   [Compaction](turn-loop/claude-invocation.md#compaction)). Rate-limit
+   [Compaction](claude-invocation.md#compaction)). Rate-limit
    and auth-failure detection is described [below](#failure-detection-and-login).
 7. Emit `LiveEvent::TurnEnd { ok, note }`. Sleep `poll_ms` to avoid
    tight loops on transient failures.
@@ -94,12 +94,12 @@ loop (`serve_loop` / `handle_turn`) has no per-role branches.
 flake sets it unconditionally for any container-deployed agent;
 see `docs/conventions.md::Hive identity` for the env stack),
 opens turn-stats sqlite, prepares the on-boot files (see
-[claude-invocation](turn-loop/claude-invocation.md#on-boot-files)),
+[claude-invocation](claude-invocation.md#on-boot-files)),
 installs claude plugins, spawns `web_ui::serve` + `vacuum::run`,
 and either drops into `serve_loop` directly (`Online`) or parks on
 the login flow first (`NeedsLogin`). (The forge notification poller
 used to be spawned here too; it is its own process now —
-`hive-forge-notify`, see [`forge.md`](forge.md).)
+`hive-forge-notify`, see [`forge.md`](../forge.md).)
 
 `spawn_todo_socket` opens the todos store and, alongside
 `todo_server::run` (the socket the out-of-process producers dial),
@@ -153,17 +153,17 @@ harness between turns.
 
 ## Sub-pages
 
-The rest lives in three topic pages under [`turn-loop/`](turn-loop/):
+The rest lives alongside this page, in three topic files:
 
-- **[claude-invocation.md](turn-loop/claude-invocation.md)** — how the harness
+- **[claude-invocation.md](claude-invocation.md)** — how the harness
   spawns `claude --print` each turn, the two-pronged compaction (reactive +
   proactive), and the on-boot files it materialises (`--mcp-config`,
   `--system-prompt-file`).
-- **[config.md](turn-loop/config.md)** — the optional per-agent knobs the meta
+- **[config.md](config.md)** — the optional per-agent knobs the meta
   flake wires in (reference docs, icon, passwordless sudo, dashboard links,
   custom static files, connectivity overrides, claude plugins, cargo message
   filtering).
-- **[mcp.md](turn-loop/mcp.md)** — the MCP tool surface claude sees: core tools,
+- **[mcp.md](mcp.md)** — the MCP tool surface claude sees: core tools,
   privileged tool groups, self-wake, authoritative state, the tool envelope,
   and the built-in tool whitelist.
 

docs/turn-loop/claude-invocation.md

@@ -116,7 +116,7 @@ window with two triggers baked into its `run`:
   *still* overflows, `run` surfaces `Error::PromptTooLong`; `drive_turn`
   then archives the session (session lifecycle stays hive-side) and the
   serve loop requeues the message so it redelivers into a fresh session
-  (see [Turn outcomes](../turn-loop.md#turn-outcomes) — the wake prompt itself is tiny, so
+  (see [Turn outcomes](README.md#turn-outcomes) — the wake prompt itself is tiny, so
   the overflow was the accumulated context the archive clears).
 - **Proactive** — a turn finishes cleanly but the last inference's context
   size crossed the policy watermark. While the session is still healthy it