fix(portals)!: reject unknown flags in all six CLIs

Silently discarded flags produced silently wrong results: jobdanmark
with --query (its real flag is --text) returned all 13,862 jobs as if
they matched, exit 0, empty stderr - indistinguishable from a real
result set. The four bunli CLIs get an argv preflight built from each
command's own options object; linkedin and freehire validate parsed
flags against per-command known sets. help/version still pass, and
add-portal.md's existing bogus-flag-exits-1 contract now holds for the
reference implementations contributors copy. One linkedin pin updated:
"--jobage-minutes -5" now fails as UNKNOWN_FLAG (the stray -5 token)
rather than BAD_ARG - same loud-failure invariant, earlier gate. Review
finding F13 (2026-08-19), decision approved by Mads.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

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

@@ -63,6 +63,16 @@ EXAMPLES
 Personal use only — uses LinkedIn's public pages; keep volume low (LinkedIn ToS).
 `
 
+// Long-form flag names each command accepts (parseFlags resolves the short
+// aliases q/l/n to these before validation). "help"/"h" pass so `search --help`
+// still prints usage.
+const KNOWN_FLAGS: Record<string, Set<string>> = {
+  search: new Set([
+    "location", "query", "jobage", "jobage-minutes", "remote", "page", "limit", "format", "help", "h",
+  ]),
+  detail: new Set(["format", "help", "h"]),
+}
+
 async function main(): Promise<number> {
   const argv = process.argv.slice(2)
   const flags = parseFlags(argv)
@@ -73,6 +83,25 @@ async function main(): Promise<number> {
     return cmd ? 0 : 1
   }
 
+  // Reject unknown flags instead of silently discarding them: a discarded
+  // filter changes what the search returns with no error (a wrong flag name
+  // once returned an entire portal's database as if it matched the query).
+  // add-portal.md's contract requires a bogus flag to exit 1 with a JSON
+  // error on stderr.
+  const knownFlags = KNOWN_FLAGS[cmd]
+  if (knownFlags) {
+    for (const key of Object.keys(flags)) {
+      if (key === "_" || knownFlags.has(key)) continue
+      process.stderr.write(
+        JSON.stringify({
+          error: `unknown flag --${key} for '${cmd}' - flags are never silently ignored, because a discarded filter changes what the search returns; see --help for the supported flags`,
+          code: "UNKNOWN_FLAG",
+        }) + "\n",
+      )
+      return 1
+    }
+  }
+
   if (cmd === "search") {
     const location = typeof flags.location === "string" ? flags.location : undefined
     if (!location) {