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/SKILL.md

@@ -50,6 +50,7 @@ Key flags:
 - `--location <text>` / `-l <text>` — **required.** A LinkedIn place string, e.g. `"Mumbai, Maharashtra, India"`, `"Berlin, Germany"`, `"London, United Kingdom"`, or `"Remote"`.
 - `--query <text>` / `-q <text>` — keyword search (title, skill, role). Recommended.
 - `--jobage <days>` — posted within N days: `1`, `7`, `14`, `30`. Omit for all postings.
+- `--jobage-minutes <n>` — posted within N minutes (sub-day precision, e.g. `30`). Conflicts with `--jobage` — pass only one.
 - `--remote <mode>` — `remote`, `hybrid`, or `onsite` (workplace-type filter).
 - `--page <n>` — page number (1-indexed, 10 results per page).
 - `--limit <n>` / `-n <n>` — cap total results emitted (client-side).
@@ -77,6 +78,9 @@ bun run .agents/skills/linkedin-search/cli/src/cli.ts search -q "product manager
 # Any role, fully remote
 bun run .agents/skills/linkedin-search/cli/src/cli.ts search -q "paralegal" -l "Remote" --format table
 
+# Engineer roles, remote, posted in the last 30 minutes
+bun run .agents/skills/linkedin-search/cli/src/cli.ts search -q "engineer" -l "Remote" --jobage-minutes 30 --format table
+
 # Full details for a specific job
 bun run .agents/skills/linkedin-search/cli/src/cli.ts detail 4426311357 --format plain
 ```