C0: wire Palette delegation into run.Executor (skill__/agent__ tools)

The first cutover prerequisite: the executor now turns an agent's SkillPalette /
SubAgentPalette into delegation tools so a mort agent that delegates works
through run.Executor (the piece the `.agent run` canary needs beyond the
already-wired audit/budget).

- run/palette.go: addDelegationTools builds a skill__<name> tool (structured
  inputs) per SkillPalette entry and an agent__<name> tool (prompt) per
  SubAgentPalette entry, each invoking run.Ports.Palette as a CHILD of the
  current run (parentRunID = inv.RunID, inheriting caller + channel). A non-ok
  child status is surfaced to the parent with the partial output. nil-safe: no
  PaletteSource or empty palette → no delegation tools (unchanged behavior).
- executor.go: call it right after building the low-level toolbox.

Tests: the model calls skill__helper → routed through Palette with the right
name/caller/inputs/parent; nil palette → run still works.

Deferred to C0b (the remaining run.Ports executor wiring): Critic (soft-timeout
monitor + deadline binding + steer), Delivery (output egress for surfaces that
need executor-side delivery), Checkpointer (needs a majordomo message-history
hook to snapshot resumable state). The `.agent run` canary delivers its returned
Result.Output itself, so these aren't on its critical path.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

run/executor.go

@@ -168,6 +168,14 @@ func (e *Executor) Run(ctx context.Context, ra RunnableAgent, inv tool.Invocatio
 		return res
 	}
 
+	// Add skill__/agent__ delegation tools from the agent's palette (nil-safe:
+	// no PaletteSource or empty palette → no delegation tools).
+	if err := addDelegationTools(toolbox, ra, inv, e.cfg.Ports.Palette); err != nil {
+		res.Err = fmt.Errorf("build delegation tools: %w", err)
+		e.finishAudit(ctx, rec, "error", res, started, res.Err)
+		return res
+	}
+
 	// Run context: bound by MaxRuntime, detached from the caller's deadline so a
 	// lane/queue wait doesn't eat the run budget (mort's V10 lesson). Caller
 	// cancellation still propagates via MergeCancellation. Created BEFORE the