feat!: unify mosaic CLI — native launcher, no bin/ directory

BREAKING CHANGE: ~/.config/mosaic/bin/ is removed entirely.
The mosaic npm CLI is now the only executable.

## What changed

- **bin/ → deleted**: All scripts moved to tools/_scripts/ (internal)
- **mosaic-launch → deleted**: Launcher logic is native TypeScript
  in packages/cli/src/commands/launch.ts
- **mosaic.ps1 → deleted**: PowerShell launcher removed
- **Framework install.sh**: Complete rewrite with migration system
- **Version tracking**: .framework-version file (schema v2)
- **Migration v1→v2**: Auto-removes bin/, cleans old PATH entries
  from shell profiles

## Native TypeScript launcher (commands/launch.ts)

All runtime launch logic ported from bash:
- Runtime prompt builder (AGENTS.md + RUNTIME.md + USER.md + TOOLS.md)
- Mission context injection (reads .mosaic/orchestrator/mission.json)
- PRD status injection (scans docs/PRD.md)
- Pre-flight checks (MOSAIC_HOME, AGENTS.md, SOUL.md, runtime binary)
- Session lock management with signal cleanup
- Per-runtime launch: Claude, Codex, OpenCode, Pi
- Yolo mode flags per runtime
- Pi skill discovery + extension loading
- Framework management (init, doctor, sync, bootstrap) delegates
  to tools/_scripts/ bash implementations

## Installer

- tools/install.sh: detects framework by .framework-version or AGENTS.md
- Framework install.sh: migration system with schema versioning
- Forward-compatible: add migrations as numbered blocks
- No PATH manipulation for framework (npm bin is the only PATH entry)

tools/install.sh

@@ -114,10 +114,10 @@ version_lt() {
 }
 
 framework_version() {
-  # Read VERSION from the installed mosaic launcher
-  local mosaic_bin="$MOSAIC_HOME/bin/mosaic"
-  if [[ -f "$mosaic_bin" ]]; then
-    grep -m1 '^VERSION=' "$mosaic_bin" 2>/dev/null | cut -d'"' -f2 || true
+  # Read framework schema version stamp
+  local vf="$MOSAIC_HOME/.framework-version"
+  if [[ -f "$vf" ]]; then
+    cat "$vf" 2>/dev/null || true
   fi
 }
 
@@ -145,7 +145,7 @@ if [[ "$FLAG_FRAMEWORK" == "true" ]]; then
 
   FRAMEWORK_CURRENT="$(framework_version)"
   HAS_FRAMEWORK=false
-  [[ -d "$MOSAIC_HOME/bin" ]] && [[ -f "$MOSAIC_HOME/bin/mosaic" ]] && HAS_FRAMEWORK=true
+  [[ -f "$MOSAIC_HOME/AGENTS.md" ]] || [[ -f "$MOSAIC_HOME/.framework-version" ]] && HAS_FRAMEWORK=true
 
   if [[ -n "$FRAMEWORK_CURRENT" ]]; then
     dim "  Installed: framework v${FRAMEWORK_CURRENT}"
@@ -202,13 +202,8 @@ if [[ "$FLAG_FRAMEWORK" == "true" ]]; then
     ok "Framework installed"
     echo ""
 
-    # Ensure framework bin is on PATH
-    FRAMEWORK_BIN="$MOSAIC_HOME/bin"
-    if [[ ":$PATH:" != *":$FRAMEWORK_BIN:"* ]]; then
-      warn "$FRAMEWORK_BIN is not on your PATH"
-      dim "  The 'mosaic' launcher lives here. Add to your shell rc:"
-      dim "  export PATH=\"$FRAMEWORK_BIN:\$PATH\""
-    fi
+    # Framework bin is no longer needed on PATH — the npm CLI delegates
+    # to mosaic-launch directly via its absolute path.
   fi
 fi
 
@@ -290,7 +285,6 @@ if [[ "$FLAG_CLI" == "true" ]]; then
     # PATH check for npm prefix
     if [[ ":$PATH:" != *":$PREFIX/bin:"* ]]; then
       warn "$PREFIX/bin is not on your PATH"
-      dim "  The 'mosaic' TUI/gateway CLI lives here (separate from the launcher)."
       dim "  Add to your shell rc:  export PATH=\"$PREFIX/bin:\$PATH\""
     fi
   fi
@@ -303,28 +297,9 @@ fi
 if [[ "$FLAG_CHECK" == "false" ]]; then
   step "Summary"
 
-  echo "  ${BOLD}Framework launcher:${RESET}  $MOSAIC_HOME/bin/mosaic"
-  echo "    ${DIM}mosaic claude, mosaic yolo claude, mosaic pi, mosaic doctor, …${RESET}"
+  echo "  ${BOLD}mosaic:${RESET}          $PREFIX/bin/mosaic"
+  dim "  Framework data:  $MOSAIC_HOME/"
   echo ""
-  echo "  ${BOLD}npm CLI (TUI):${RESET}       $PREFIX/bin/mosaic"
-  echo "    ${DIM}mosaic tui, mosaic login, mosaic wizard, mosaic update, …${RESET}"
-  echo ""
-
-  # Warn if there's a naming collision (both on PATH)
-  FRAMEWORK_BIN="$MOSAIC_HOME/bin"
-  if [[ ":$PATH:" == *":$FRAMEWORK_BIN:"* ]] && [[ ":$PATH:" == *":$PREFIX/bin:"* ]]; then
-    # Check which one wins
-    WHICH_MOSAIC="$(command -v mosaic 2>/dev/null || true)"
-    if [[ -n "$WHICH_MOSAIC" ]]; then
-      dim "  Active 'mosaic' binary: $WHICH_MOSAIC"
-      if [[ "$WHICH_MOSAIC" == "$FRAMEWORK_BIN/mosaic" ]]; then
-        dim "  (Framework launcher takes priority — this is correct)"
-      else
-        warn "npm CLI shadows the framework launcher!"
-        dim "  Ensure $FRAMEWORK_BIN appears BEFORE $PREFIX/bin in your PATH."
-      fi
-    fi
-  fi
 
   # First install guidance
   if [[ ! -f "$MOSAIC_HOME/SOUL.md" ]]; then