feat: add multi-runtime support (coord run, prdy --codex) and next-task capsule

- coord/prdy subcommands now accept --claude/--codex runtime flags
- New `mosaic coord run` generates continuation context and launches
  selected runtime, replacing manual copy/paste workflow
- Next-task capsule (.mosaic/orchestrator/next-task.json) provides
  machine-readable execution context for deterministic session launches
- Codex strict orchestrator profile added to runtime/codex/RUNTIME.md
- Orchestrator protocol updated with between-session run flow
- New smoke-test.sh for orchestration behavior verification

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tools/orchestrator/session-run.sh

@@ -0,0 +1,80 @@
+#!/usr/bin/env bash
+set -euo pipefail
+#
+# session-run.sh — Generate continuation context and launch target runtime.
+#
+# Usage:
+#   session-run.sh [--project <path>] [--milestone <id>] [--print]
+#
+# Behavior:
+# - Builds continuation prompt + next-task capsule.
+# - Launches selected runtime (default: claude, override via MOSAIC_COORD_RUNTIME).
+# - For codex, injects strict orchestration kickoff to reduce clarification loops.
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR/_lib.sh"
+
+PROJECT="."
+MILESTONE=""
+PRINT=false
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    --project)   PROJECT="$2"; shift 2 ;;
+    --milestone) MILESTONE="$2"; shift 2 ;;
+    --print)     PRINT=true; shift ;;
+    -h|--help)
+      cat <<'USAGE'
+Usage: session-run.sh [--project <path>] [--milestone <id>] [--print]
+
+Options:
+  --project <path>   Project directory (default: CWD)
+  --milestone <id>   Force specific milestone context
+  --print            Print launch prompt only (no runtime launch)
+USAGE
+      exit 0
+      ;;
+    *) echo "Unknown option: $1" >&2; exit 1 ;;
+  esac
+done
+
+PROJECT="${PROJECT/#\~/$HOME}"
+PROJECT="$(cd "$PROJECT" && pwd)"
+
+_require_jq
+require_mission "$PROJECT"
+
+runtime="$(coord_runtime)"
+launch_cmd="$(coord_launch_command)"
+
+continue_cmd=(bash "$SCRIPT_DIR/continue-prompt.sh" --project "$PROJECT")
+if [[ -n "$MILESTONE" ]]; then
+  continue_cmd+=(--milestone "$MILESTONE")
+fi
+
+continuation_prompt="$(MOSAIC_COORD_RUNTIME="$runtime" "${continue_cmd[@]}")"
+
+if [[ "$runtime" == "codex" ]]; then
+  launch_prompt="$(build_codex_strict_kickoff "$PROJECT" "$continuation_prompt")"
+else
+  launch_prompt="$continuation_prompt"
+fi
+
+if [[ "$PRINT" == true ]]; then
+  echo "$launch_prompt"
+  exit 0
+fi
+
+echo -e "${C_CYAN}Launching orchestration runtime: ${launch_cmd}${C_RESET}"
+echo -e "${C_CYAN}Project:${C_RESET} $PROJECT"
+echo -e "${C_CYAN}Capsule:${C_RESET} $(next_task_capsule_path "$PROJECT")"
+
+cd "$PROJECT"
+if [[ "$runtime" == "claude" ]]; then
+  exec "$MOSAIC_HOME/bin/mosaic" claude "$launch_prompt"
+elif [[ "$runtime" == "codex" ]]; then
+  exec "$MOSAIC_HOME/bin/mosaic" codex "$launch_prompt"
+fi
+
+echo -e "${C_RED}Unsupported coord runtime: $runtime${C_RESET}" >&2
+exit 1