feat(web): add fuzzy slash command discovery

packages/client/ui-command/src/client/service.ts

@@ -2,9 +2,10 @@
  * CommandService (`ctx.command`): the '/' command source over the
  * session-keyed directory, the client-contribution registry, and the
  * per-session popupSelect controllers. Candidate synthesis merges the host
- * catalog with contributions by availability, then query/position filtering;
- * a host/contribution name collision fails loud. Every execute addresses the
- * session's agent by sessionId — sessions are always agent-backed.
+ * catalog with contributions by availability, then fuzzy query/position
+ * filtering; a host/contribution name collision fails loud. Every execute
+ * addresses the session's agent by sessionId — sessions are always
+ * agent-backed.
  */
 import { Service } from 'cordis'
 import type { Context } from 'cordis'
@@ -27,6 +28,69 @@ interface LiveState {
   readonly popups: Map<SessionId, PopupSelectController<ClientSessionContext>>
 }
 
+/** One fuzzy match with its stable source position. */
+interface RankedCandidate {
+  readonly candidate: SlashCandidate
+  readonly index: number
+  readonly prefix: boolean
+  readonly score: number
+}
+
+/** Extra weight for command-name starts and separator boundaries. */
+function boundaryBonus(name: string, index: number): number {
+  return index === 0 || name.charAt(index - 1) === '-' || name.charAt(index - 1) === '_' ? 8 : 0
+}
+
+/**
+ * Score the strongest ordered-subsequence alignment in O(name × query).
+ * Boundary and adjacent matches earn weight; skipped and leading characters
+ * cost weight.
+ */
+function fuzzyScore(name: string, query: string): number | undefined {
+  if (query === '') return 0
+  if (query.length > name.length) return undefined
+  const noMatch = Number.NEGATIVE_INFINITY
+  let previous = Array<number>(name.length).fill(noMatch)
+  for (let index = 0; index < name.length; index++) {
+    if (name.charAt(index) === query.charAt(0)) previous[index] = 1 + boundaryBonus(name, index) - index
+  }
+  for (let queryIndex = 1; queryIndex < query.length; queryIndex++) {
+    const current = Array<number>(name.length).fill(noMatch)
+    let bestGapped = noMatch
+    for (let index = 0; index < name.length; index++) {
+      const gappedIndex = index - 2
+      if (gappedIndex >= 0) {
+        const prior = previous[gappedIndex] ?? noMatch
+        if (prior !== noMatch) bestGapped = Math.max(bestGapped, prior + gappedIndex)
+      }
+      if (name.charAt(index) !== query.charAt(queryIndex)) continue
+      const bonus = 1 + boundaryBonus(name, index)
+      const adjacent = index > 0 ? previous[index - 1] ?? noMatch : noMatch
+      if (adjacent !== noMatch) current[index] = adjacent + bonus + 4
+      if (bestGapped !== noMatch) current[index] = Math.max(current[index] ?? noMatch, bestGapped + bonus + 1 - index)
+    }
+    previous = current
+  }
+  let best = noMatch
+  for (const score of previous) best = Math.max(best, score)
+  return best === noMatch ? undefined : best
+}
+
+/** Case-insensitive fuzzy filtering with stable ordering for equal matches. */
+function fuzzyCandidates(candidates: readonly SlashCandidate[], rawQuery: string): readonly SlashCandidate[] {
+  const query = rawQuery.toLowerCase()
+  if (query === '') return candidates
+  const ranked: RankedCandidate[] = []
+  candidates.forEach((candidate, index) => {
+    const name = candidate.name.toLowerCase()
+    const score = fuzzyScore(name, query)
+    if (score !== undefined) ranked.push({ candidate, index, prefix: name.startsWith(query), score })
+  })
+  ranked.sort((left, right) =>
+    Number(right.prefix) - Number(left.prefix) || right.score - left.score || left.index - right.index)
+  return ranked.map(match => match.candidate)
+}
+
 /** Command surface: session-keyed directory + '/' source + contribution registry + per-session popups. */
 export class CommandService extends Service implements CommandServiceContract {
   static inject = ['slash', 'sessions', 'connection']
@@ -147,7 +211,7 @@ export class CommandService extends Service implements CommandServiceContract {
     }
   }
 
-  /** Menu candidates: host catalog + contribution availability, then query/position filtering. */
+  /** Menu candidates: host catalog + contribution availability, then position filtering and fuzzy name ranking. */
   private async candidates(session: ClientSessionContext, req: CandidateRequest): Promise<readonly SlashCandidate[]> {
     const list = await this.directory.ensureReady(session.sessionId, req.signal)
     const rows: SlashCandidate[] = []
@@ -163,9 +227,10 @@ export class CommandService extends Service implements CommandServiceContract {
       }
       rows.push({ name: contribution.name, description: contribution.description })
     }
-    return rows
-      .filter(c => c.name.startsWith(req.query))
-      .filter(c => req.position === 'leading' || c.hint === undefined)
+    return fuzzyCandidates(
+      rows.filter(c => req.position === 'leading' || c.hint === undefined),
+      req.query,
+    )
   }
 
   /** Decision table, menu column: contribution/decorated-host → popup; host input → claim; host bare → detached execute. */