Postbox -> TelegramEngine wave 10: StorageFileListPanelComponent drop

Closes the last future-wave candidate from wave 8 by eliminating the
Icon.media(Media, ...) enum case in StorageFileListPanelComponent.swift
and dropping import Postbox. StorageUsageScreen (the module as a whole)
is now fully Postbox-free.

Icon enum split:
  case media(Media, TelegramMediaImageRepresentation)  ->
    case mediaFile(TelegramMediaFile, TelegramMediaImageRepresentation)
    case mediaImage(TelegramMediaImage, TelegramMediaImageRepresentation)

Equatable rewritten as switch-over-tuple with id-based equality per
concrete type (lFile.fileId == rFile.fileId / lImage.imageId ==
rImage.imageId), same semantics as the old media.id comparison.

Binding site: `if case let .media(media, representation)` +
`as? TelegramMediaFile` / `as? TelegramMediaImage` downcasts ->
compound case-binding `case let .mediaFile(_, representation), let
.mediaImage(_, representation):` to lift the shared representation
variable, plus an inner switch for the setSignal branch. The compiler-
enforced exhaustiveness of the split improves call-site safety.

Construction sites (2): `.media(file, representation)` -> `.mediaFile(
file, representation)`, `.media(image, representation)` -> `.mediaImage(
image, representation)`.

Placeholder fixup:
  messageId: EngineMessage.Id(peerId: PeerId(namespace: PeerId.Namespace
    ._internalFromInt32Value(0), id: PeerId.Id._internalFromInt64Value(0)
    ), namespace: 0, id: 0)
  ->
  messageId: EngineMessage.Id(peerId: component.context.account.peerId,
    namespace: 0, id: 0)

Inside a measureItem layout-measurement instance. Caught by second-pass
build failure `cannot find 'PeerId' in scope`. PeerId / PeerId.Namespace
/ PeerId.Id are raw Postbox types (not TelegramCore typealiases —
consistent with wave 9's MessageId -> EngineMessage.Id fixup). Using
context.account.peerId is semantically equivalent for the measurement
use case (messageId only feeds image-fetch userLocation and Equatable
comparison, neither exercised for this standalone instance).

Net: 1 file changed, +22 / -29 lines.

Plan: docs/superpowers/plans/2026-04-20-postbox-to-telegramengine-wave-10.md

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -256,6 +256,24 @@ Net: 1 file changed, +30 / -54. Build verified green (27 actions, cached).
 
 Plan / record: `docs/superpowers/plans/2026-04-20-postbox-to-telegramengine-wave-9.md`.
 
+### Wave 10 outcome (2026-04-20)
+
+Closes the second (and last) future-wave candidate from wave 8: eliminates `StorageFileListPanelComponent.swift`'s `Icon.media(Media, TelegramMediaImageRepresentation)` enum case. **`StorageUsageScreen` (the module as a whole) is now fully Postbox-free** — the other in-module file (`StorageUsageScreen.swift`) landed in wave 9.
+
+**Split the enum case.** `Icon.media(Media, TelegramMediaImageRepresentation)` → two concrete cases `case mediaFile(TelegramMediaFile, TelegramMediaImageRepresentation)` + `case mediaImage(TelegramMediaImage, TelegramMediaImageRepresentation)`. Lossless split: the two construction sites already knew the concrete subtype (`imageIconValue = .media(file, representation)` from a `as? TelegramMediaFile` branch, `.media(image, representation)` from a `as? TelegramMediaImage` branch), and the consumer binding site immediately downcast via `as?` to pick which `setSignal(...)` flavor to call. New split removes the downcast; exhaustiveness-checked switch is both safer and terser.
+
+**Equatable rewritten.** Old: manual outer-`switch` + inner `if case` dispatch, comparing media by `media.id` only. New: switch-over-tuple `(lhs, rhs)` with id-based equality per concrete type (`lFile.fileId == rFile.fileId`, `lImage.imageId == rImage.imageId`). Same id-based equality semantics as before.
+
+**Binding-site rewrite.** Old: `if case let .media(media, representation) = component.icon { ... if let file = media as? TelegramMediaFile { ... } else if let image = media as? TelegramMediaImage { ... } }`. New: a compound case-binding pattern `case let .mediaFile(_, representation), let .mediaImage(_, representation):` lifts the shared `representation` variable, then an inner switch dispatches to the right `setSignal` branch. Works because both cases carry the same `TelegramMediaImageRepresentation` payload type; Swift allows compound case patterns when the bindings have identical types.
+
+**Placeholder `PeerId(...)` construction fixup.** Second-pass build failure after dropping `import Postbox` surfaced a placeholder `PeerId(namespace: PeerId.Namespace._internalFromInt32Value(0), id: PeerId.Id._internalFromInt64Value(0))` in the `measureItem` layout-measurement instance at former line 1062. Naming `PeerId`, `PeerId.Namespace`, and `PeerId.Id` all require `import Postbox` (these are raw Postbox types, not TelegramCore typealiases — consistent with wave 9's `MessageId` → `EngineMessage.Id` fixup). Replaced with `component.context.account.peerId` (a real `EnginePeer.Id` already in scope). Semantically equivalent since the measurement instance's `messageId` is only used for `.peerId` extraction inside image-fetch `userLocation` and for Equatable comparison (the measurement instance isn't compared to anything).
+
+**Lesson.** Placeholder `PeerId(...)` / `MessageId(peerId:...)` constructions in layout-measurement code are a recurring trap for de-Postbox work. Common pattern in this codebase: construct a dummy component instance purely to call `.update(...)` and read back the returned size. The dummy values are not used meaningfully but naming the types pins `import Postbox`. When de-Postboxing, grep for `PeerId(namespace:`/`MessageId(peerId:` with all-zero args and replace with any convenient real value in scope (`context.account.peerId` is almost always available).
+
+Net: 1 file changed, +22 / -29 lines (−7 simplification — new switch-over-tuple Equatable is both terser and more idiomatic).
+
+Plan / record: `docs/superpowers/plans/2026-04-20-postbox-to-telegramengine-wave-10.md`.
+
 ### Modules currently free of `import Postbox` (running tally)
 
 Consumer modules that no longer import Postbox, across all waves and standalone commits:
@@ -271,6 +289,7 @@ Consumer modules that no longer import Postbox, across all waves and standalone
 - `SaveToCameraRoll` (wave 3)
 - `SecureIdVerificationDocumentsContext` (wave 5)
 - **Wave 6 batch: 189 additional modules** — see `git show 7b2b74e79b --stat` for the commit that swept unused `import Postbox` lines across 183 files in 16 consumer submodules. Not individually enumerated here for brevity.
+- `StorageUsageScreen` (waves 8–10)
 
 ### Known future-wave candidates