add compile-time interface assertions for public types (task c4)

Extend the var _ Interface = (*Concrete)(nil) coverage started in j3 to
cover the remaining public types not yet guarded:

- *file.FdFile → file.File (file/file.go)
- streamrow.Row → globalfilter.Candidate (streamrow/row.go; adds
  globalfilter import — no cycle since globalfilter does not import streamrow)
- *streamrow.RingBuffer → eventstream.Source
  (tui/eventstream/ringbuffer.go; already a type alias for streamrow.RingBuffer)
- *probemanager.Manager → tui/probes.Manager (tui/probes/model.go)
- All 9 generated *types.*Event types → event.Event in the new file
  internal/event/interface_assertions.go (non-generated, lives in the event
  package which already imports types, so no new import cycle)

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

5 files changed, 78 insertions, 0 deletions

diff --git a/internal/event/interface_assertions.go b/internal/event/interface_assertions.go
new file mode 100644
index 0000000..77a43ea
--- /dev/null
+++ b/internal/event/interface_assertions.go
@@ -0,0 +1,44 @@
+package event
+
+import "ior/internal/types"
+
+// --- compile-time interface satisfaction assertions ---
+//
+// Every generated concrete event type in internal/types must satisfy the Event
+// interface (which composes EventIdentity and EventLifecycle). These assertions
+// live in the event package rather than in the generated file so they are not
+// overwritten by mage generate. The event package already imports types, so no
+// new import cycle is introduced.
+
+var (
+	// *types.OpenEvent is the most common event type; it carries open-syscall
+	// enter-event data (fd, flags, pathname).
+	_ Event = (*types.OpenEvent)(nil)
+
+	// *types.NullEvent is used for tracepoints that carry no extra payload
+	// beyond the base header fields.
+	_ Event = (*types.NullEvent)(nil)
+
+	// *types.FdEvent carries a single file-descriptor field (close, dup, etc.).
+	_ Event = (*types.FdEvent)(nil)
+
+	// *types.RetEvent is the exit-side event for all syscalls; it carries the
+	// kernel return value.
+	_ Event = (*types.RetEvent)(nil)
+
+	// *types.NameEvent carries a single filename field (unlink, mkdir, etc.).
+	_ Event = (*types.NameEvent)(nil)
+
+	// *types.PathEvent carries a pathname field for path-only syscalls.
+	_ Event = (*types.PathEvent)(nil)
+
+	// *types.FcntlEvent carries the fcntl command and argument fields.
+	_ Event = (*types.FcntlEvent)(nil)
+
+	// *types.Dup3Event carries the old and new file-descriptor fields for dup3.
+	_ Event = (*types.Dup3Event)(nil)
+
+	// *types.OpenByHandleAtEvent carries the mount-fd and flags for
+	// open_by_handle_at syscalls.
+	_ Event = (*types.OpenByHandleAtEvent)(nil)
+)
diff --git a/internal/file/file.go b/internal/file/file.go
index fc9c320..f933d69 100644
--- a/internal/file/file.go
+++ b/internal/file/file.go
@@ -217,3 +217,11 @@ func (f pathnameFile) String() string {
 
 	return sb.String()
 }
+
+// --- compile-time interface satisfaction assertions ---
+//
+// *FdFile is the primary public implementation of File used throughout the
+// codebase. The assertion causes a build error if FdFile drifts out of sync
+// with the File interface contract.
+
+var _ File = (*FdFile)(nil)
diff --git a/internal/streamrow/row.go b/internal/streamrow/row.go
index 457fcc0..026aa93 100644
--- a/internal/streamrow/row.go
+++ b/internal/streamrow/row.go
@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"ior/internal/event"
+	"ior/internal/globalfilter"
 	"ior/internal/types"
 )
 
@@ -121,6 +122,15 @@ func New(seq uint64, pair *event.Pair) Row {
 	return row
 }
 
+// --- compile-time interface satisfaction assertion ---
+//
+// Row must satisfy globalfilter.Candidate so the TUI eventstream model can
+// pass stream rows directly into Filter.Matches for live filtering. All
+// Candidate methods are defined on the value receiver so both Row and *Row
+// satisfy the interface; we assert the value form as it is the common usage.
+
+var _ globalfilter.Candidate = Row{}
+
 // NewWarning creates a synthetic row for non-fatal runtime warnings.
 func NewWarning(seq uint64, message string) Row {
 	now := uint64(time.Now().UnixNano())
diff --git a/internal/tui/eventstream/ringbuffer.go b/internal/tui/eventstream/ringbuffer.go
index 8644b42..8879114 100644
--- a/internal/tui/eventstream/ringbuffer.go
+++ b/internal/tui/eventstream/ringbuffer.go
@@ -15,3 +15,11 @@ const ringBufferCapacity = streamrow.RingBufferCapacity
 func NewRingBuffer() *RingBuffer {
 	return streamrow.NewRingBuffer()
 }
+
+// --- compile-time interface satisfaction assertion ---
+//
+// *RingBuffer (= *streamrow.RingBuffer) must satisfy the Source contract so
+// the TUI dashboard and stream views can receive live events without importing
+// the lower-level streamrow package directly.
+
+var _ Source = (*RingBuffer)(nil)
diff --git a/internal/tui/probes/model.go b/internal/tui/probes/model.go
index baf22e8..b7e694f 100644
--- a/internal/tui/probes/model.go
+++ b/internal/tui/probes/model.go
@@ -346,3 +346,11 @@ func truncateText(s string, limit int) string {
 	}
 	return string(runes[:limit-3]) + "..."
 }
+
+// --- compile-time interface satisfaction assertion ---
+//
+// *probemanager.Manager must satisfy the Manager interface defined in this
+// package. The tui/probes package already imports probemanager, so this
+// assertion adds no new dependency.
+
+var _ Manager = (*probemanager.Manager)(nil)