feat(linkedin-search): add --jobage-minutes for sub-day freshness windows (#302)

jobageToTPR() only emits whole-day f_TPR windows, so a search can't be
restricted to postings from the last N minutes. LinkedIn's f_TPR filters
server-side down to one-second granularity (confirmed empirically), so
this is a pure window-construction change via a new minutesToTPR()
helper - no HTML parsing changes needed.

--jobage-minutes and --jobage both express a freshness window; passing
both is rejected with CONFLICTING_AGE_FLAGS rather than one silently
overriding the other.

.agents/skills/linkedin-search/cli/src/commands/search.ts

@@ -3,6 +3,7 @@ import {
   htmlFetch,
   parseJobCards,
   jobageToTPR,
+  minutesToTPR,
   workTypeFlag,
   writeError,
   type JobCard,
@@ -12,6 +13,7 @@ export interface SearchOpts {
   query?: string
   location: string
   jobage: number
+  jobageMinutes?: number
   remote?: string // "remote" | "hybrid" | "onsite"
   page: number
   limit?: number
@@ -22,7 +24,7 @@ function buildUrl(opts: SearchOpts): string {
   const params = new URLSearchParams()
   if (opts.query) params.set("keywords", opts.query)
   if (opts.location) params.set("location", opts.location)
-  const tpr = jobageToTPR(opts.jobage)
+  const tpr = opts.jobageMinutes !== undefined ? minutesToTPR(opts.jobageMinutes) : jobageToTPR(opts.jobage)
   if (tpr) params.set("f_TPR", tpr)
   const wt = workTypeFlag(opts.remote)
   if (wt) params.set("f_WT", wt)