feat(hud): integrate Wave 2-B/2-C in format_status_line (Wave 3)

Wave 3 integrator:
- Merged all 9 parallel Wave sub-branches (Wave 0 + 1-A/B/C/D + 2-A/B/C/D/E)
- Added Wave 2-B velocity suffix + Wave 2-C cache savings suffix to cost segment
- 5 integration tests lock the Wave 3 assembly

Cost segment output examples:
  "$1.23"                              (plain, no data)
  "$1.23↗$0.08/m"                      (velocity only)
  "$1.23💰$4.56 saved"                 (savings only)
  "$1.23↗$0.08/m💰$4.56 saved"         (both)

Defensive try/except imports ensure format_status_line still works
when the optional modules are temporarily broken.

Follow-up Wave 2 modules merged but not yet wired into format_status_line:
- Wave 2-A: hud_buddy dynamic face per phase
- Wave 2-D: hud_rainbow mode label coloring
- Wave 2-E: hud_context_bar visual bar
- Wave 1-D: hud_layout fit_segments adaptive truncation

381/381 tests pass (9 Wave-level test suites + Wave 3 integration).

Closes the Wave 3 task. Part of #1464 (Wave 0 statusbar refactor effort).

Author: JeremyDev87

packages/claude-code-plugin/hooks/codingbuddy-hud.py

@@ -458,13 +458,30 @@ def format_status_line(
 
     cost_prefix = "$" if is_exact else "~$"
 
+    # Wave 3 integration: append optional Wave 2-B velocity and
+    # Wave 2-C cache-savings suffixes to the cost segment. Both
+    # helpers return empty string when they have nothing to show,
+    # so the downstream segment renders unchanged in the common case.
+    velocity_suffix = ""
+    savings_suffix = ""
+    try:
+        from hud_velocity import format_velocity_segment
+        velocity_suffix = format_velocity_segment(stdin_data, hud_state) or ""
+    except Exception:  # pragma: no cover - defensive
+        pass
+    try:
+        from hud_cache_savings import format_cache_savings
+        savings_suffix = format_cache_savings(stdin_data) or ""
+    except Exception:  # pragma: no cover - defensive
+        pass
+
     ver_str = f" v{version}" if version else ""
 
     segments = [
         f"{BUDDY_FACE} CB{ver_str}",
         f"{mode_label} {health}",
         duration,
-        f"{cost_prefix}{cost:.2f}",
+        f"{cost_prefix}{cost:.2f}{velocity_suffix}{savings_suffix}",
     ]
     if cache_segment:
         segments.append(cache_segment)

packages/claude-code-plugin/tests/test_hud.py

@@ -743,3 +743,97 @@ def test_empty_stdin_fallback(self):
         )
         assert result.returncode == 0
         assert "\u25d5\u203f\u25d5" in result.stdout
+
+
+# ========================= Wave 3 Integration Tests ========================
+
+
+class TestWave3Integration:
+    """End-to-end integration regression for Wave 2-B/2-C cost suffixes."""
+
+    _NO_PLUGINS = "/tmp/_nonexistent_plugins_wave3.json"
+
+    def test_velocity_suffix_present_when_cost_and_duration_available(self):
+        """Wave 2-B velocity suffix appears after the cost segment."""
+        stdin = {
+            "cost": {"total_cost_usd": 1.0, "total_duration_ms": 60_000},
+            "model": {"id": "claude-sonnet", "display_name": "Sonnet"},
+            "context_window": {"used_percentage": 5},
+        }
+        state = {
+            "version": "5.5.0",
+            "sessionStartTimestamp": datetime.now(timezone.utc).isoformat(),
+            "currentMode": "PLAN",
+        }
+        result = hud.format_status_line(
+            stdin, state, plugins_file=self._NO_PLUGINS
+        )
+        # $1.00 over 60s → $1.00/m (hot burn tier)
+        assert "$1.00" in result
+        assert "/m" in result
+
+    def test_savings_suffix_present_when_cache_reads_exist(self):
+        """Wave 2-C cache savings suffix appears after the cost segment."""
+        stdin = {
+            "cost": {"total_cost_usd": 1.0, "total_duration_ms": 60_000},
+            "model": {"id": "claude-opus"},
+            "context_window": {
+                "used_percentage": 50,
+                "current_usage": {
+                    "input_tokens": 1000,
+                    "cache_creation_input_tokens": 0,
+                    "cache_read_input_tokens": 1_000_000,
+                },
+            },
+        }
+        state = {
+            "version": "5.5.0",
+            "sessionStartTimestamp": datetime.now(timezone.utc).isoformat(),
+            "currentMode": "PLAN",
+        }
+        result = hud.format_status_line(
+            stdin, state, plugins_file=self._NO_PLUGINS
+        )
+        # 1M cache_read on opus → $13.50 saved
+        assert "saved" in result
+        assert "\U0001f4b0" in result  # 💰
+
+    def test_no_velocity_when_cost_missing(self):
+        """Velocity suffix is omitted when the cost payload is absent."""
+        stdin = {"context_window": {"used_percentage": 5}}
+        state = {"version": "5.5.0", "currentMode": "PLAN"}
+        result = hud.format_status_line(
+            stdin, state, plugins_file=self._NO_PLUGINS
+        )
+        assert "/m" not in result
+
+    def test_no_savings_when_cache_reads_zero(self):
+        """Savings suffix is omitted when there are no cache reads."""
+        stdin = {
+            "cost": {"total_cost_usd": 1.0, "total_duration_ms": 60_000},
+            "context_window": {
+                "used_percentage": 5,
+                "current_usage": {
+                    "input_tokens": 1000,
+                    "cache_creation_input_tokens": 0,
+                    "cache_read_input_tokens": 0,
+                },
+            },
+        }
+        state = {"version": "5.5.0", "currentMode": "PLAN"}
+        result = hud.format_status_line(
+            stdin, state, plugins_file=self._NO_PLUGINS
+        )
+        assert "saved" not in result
+
+    def test_all_wave_modules_importable(self):
+        """Sanity: every Wave 2 module is importable through lib/."""
+        import hud_buddy  # noqa: F401
+        import hud_velocity  # noqa: F401
+        import hud_cache_savings  # noqa: F401
+        import hud_rainbow  # noqa: F401
+        import hud_context_bar  # noqa: F401
+        import hud_layout  # noqa: F401
+        import hud_session  # noqa: F401
+        import hud_version  # noqa: F401
+        import hud_rate_limits  # noqa: F401