agent-loop: projection, recovery, compaction into the crate (phase 3)

The session handler is now a thin shell: three entry points in
kernel_turn.rs (run_kernel_turn / recover_turn / resolve_pending_call)
and the ChatSessionHandler. Everything that shaped a Value — projection,
recovery, compaction mechanics, the LLM loop, message building — lives
in agent-loop or behind a loop_adapters trait.

agent-loop:
- projection/ (mod + media): stored history -> wire messages, the one
  place provider divergence lives; well-formedness contract, DTL
  injections (append-only), media parts. LinearAssembler is now a
  Projection + ProjectionHooks config, not its own implementation
- recovery.rs: reap interrupted batches -> resolve the deepest frame's
  non-terminal calls (Running by policy + RestartHint, AwaitingHuman
  re-asked) -> un-wedge finished children -> cascade up, every frame on
  its own agent (B3)
- compaction.rs: split point (never assistant+tool group), transcript,
  SUMMARY_PREFIX/preamble/template, the no-tools model call, summary row
- manager: resolve_pending (gate skipped, real ToolContext, then
  continue incl. sub-agent); start_loop used by recovery; LiveInput
- delegate: AsyncExecutor + StoreSink for mode:async (durable cron row,
  result delivered back into the parent conversation)
- kernel/context/store: support the above (TurnScope via Extensions,
  frame lookups, aligned result-text semantics)

skald-core:
- loop_adapters: UserLoopRuntime (D12 - one LoopManager per user),
  TurnScope (per-turn state in the Extensions type-map; no scope is
  denied), projection_cfg/media_source/tool_digest (Skald's projection
  knobs without owning projection code), async_task (CronExecutor +
  DurableSink)
- session/handler: stripped to mod.rs + kernel_turn.rs + config.rs +
  interface_tools.rs + media.rs; deleted agent_dispatch, approval,
  dispatch, emitter, gate, llm_call, llm_loop, message_builder,
  messages, outcome, resume
- compactor.rs: policy only (threshold, model pick, CompactionEvent);
  mechanics are the crate's

CLAUDE.md updated (recovery, compaction, sub-agents, approval gate,
projection sections now describe the crate-owned flow).

crates/skald-core/src/db/chat_history.rs

@@ -192,7 +192,7 @@ pub async fn for_stack_all(
 }
 
 /// Ok messages for a stack frame whose id is strictly greater than `after_id`,
-/// ordered chronologically.  Used by `build_openai_messages` when a compaction
+/// ordered chronologically.  Used by the projection when a compaction
 /// summary exists: only the "raw" messages after the summary boundary are loaded.
 pub async fn for_stack_since(
     pool:             &SqlitePool,

crates/skald-core/src/db/chat_summaries.rs

@@ -12,7 +12,7 @@ pub struct ChatSummary {
     pub stack_id:                i64,
     pub content:                 String,
     /// All chat_history rows with `id <= covers_up_to_message_id` are covered
-    /// by this summary. `build_openai_messages` loads only rows *after* this id.
+    /// by this summary. The projection loads only rows *after* this id.
     pub covers_up_to_message_id: i64,
     pub created_at:              String,
 }