render pasted images inline with lightbox expansion (T-236, T-254, D-89)

A pasted-image @<path> token now renders as an inline, keyboard-activatable
thumbnail in the Claude conversation that opens the full image in the lightbox;
the composer's attachment chips use the same (larger, 44px) thumbnail. New
ImageThumbnail + openImageLightbox in the Claude layer; ClideMarkdown gains an
onImageToken builder seam (mirroring onRecordTap) that drops a WidgetSpan into
the text flow — it owns no Image.file/lightbox, staying generic. Missing files
degrade to a placeholder; render-only (the sent text + copyText are unchanged).

Resolves the conflicting T-236 (inline thumbnail) / T-254 (image card) designs
into the hybrid the user chose; recorded as D-89.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

governance/README.md

@@ -130,6 +130,7 @@ You might also want, project-permitting:
 - [D-86: MCP tool surface — full clide namespace generated from the co-registered command registry](decisions/architecture.md#d-86-mcp-tool-surface--full-clide-namespace-generated-from-the-co-registered-command-registry) — _architecture_
 - [D-87: Output/log dock — bottom, toggled, read-only (logs + problems)](decisions/architecture.md#d-87-outputlog-dock--bottom-toggled-read-only-logs--problems) — _architecture_
 - [D-88: clide-owned anchored popover + menu primitive](decisions/design.md#d-88-clide-owned-anchored-popover--menu-primitive) — _design_
+- [D-89: inline pasted-image thumbnails that expand to the lightbox](decisions/design.md#d-89-inline-pasted-image-thumbnails-that-expand-to-the-lightbox) — _design_
 
 ## Open questions