feat(web): redesign Knowledge as an editable wiki

Replaces the read-only stats dashboard with a three-pane wiki: a
navigator tree (group by folder/type/tag/entity), a reader/editor with
bare-slug auto-linking and revision history + diff, and a context rail
for backlinks and related notes. Adds a Cleanup mode for the drift
tools (duplicates, tag manager, orphans, trash) and a Cmd+K quick-open.

Also:
- Adds a real landing view (hero count, KPI row, Nomos-share meter,
  recently-updated, busiest tags) in place of the old "Select a note"
  empty state, and extends the design pass across the tree/reader/rail
  (kind icons instead of repeated text badges, accent-bar selection,
  constrained prose measure).
- Guards every note-selection path behind a confirm when there's an
  unsaved edit in progress, so switching notes can no longer silently
  discard a draft.
- Extracts the markdown-rendering CSS duplicated across ChatThread,
  EntityDetailContent, and the new WikiReader into a shared
  .markdown-body class in app.css, with ChatThread keeping only its
  decorative deltas.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/lib/components/knowledge/kinds.ts

@@ -0,0 +1,50 @@
+// Per-kind presentation, shared by the tree, the overview, and anywhere else
+// a note's kind needs to be shown at a glance.
+//
+// Kind is encoded by **icon shape**, not colour. Three categories would be a
+// categorical palette, and at the 12px mark size the tree uses, colour alone
+// is the least reliable channel there is — it fails for colour-vision
+// deficiency, and small low-chroma marks on a dark surface are hard for
+// anyone to tell apart. Distinct silhouettes are legible at any size, in any
+// theme, for every reader. Colour is left to carry state (selection, the
+// agent badge), where it isn't the only thing distinguishing two items.
+//
+// It also fixes a plain redundancy: the tree previously stamped a literal
+// "document" text badge on every row, which in a folder of 20 documents is
+// 20 repetitions of the same word and no information at all.
+import FileTextIcon from '@lucide/svelte/icons/file-text'
+import MicroscopeIcon from '@lucide/svelte/icons/microscope'
+import ListChecksIcon from '@lucide/svelte/icons/list-checks'
+import type { Component } from 'svelte'
+
+export type NoteKind = 'document' | 'investigation' | 'runbook'
+
+export interface KindMeta {
+  icon: Component
+  label: string
+  /** Plural, for counts and section headings. */
+  plural: string
+}
+
+const FALLBACK: KindMeta = { icon: FileTextIcon, label: 'note', plural: 'notes' }
+
+const KIND_META: Record<NoteKind, KindMeta> = {
+  document: { icon: FileTextIcon, label: 'document', plural: 'documents' },
+  investigation: { icon: MicroscopeIcon, label: 'investigation', plural: 'investigations' },
+  runbook: { icon: ListChecksIcon, label: 'runbook', plural: 'runbooks' }
+}
+
+// Tolerates an unknown kind rather than throwing — `kind` comes from the
+// entity's type column, which the ontology could grow a fourth value for
+// without this file knowing.
+export function kindMeta(kind: string): KindMeta {
+  return KIND_META[kind as NoteKind] ?? FALLBACK
+}
+
+// True for notes last written by the agent rather than a human. Two spellings
+// exist in the live data: 'nomos-agent' (written via the MCP upsert_knowledge
+// tool) and 'agent:mcp' (the actor label the HTTP API records when the same
+// agent calls in over REST with the MCP bearer token).
+export function isAgentAuthored(editedBy: string): boolean {
+  return editedBy === 'nomos-agent' || editedBy === 'agent:mcp'
+}