fix: NaN filter bypass in LinkedIn CLI --jobage/--page/--limit flags (#35)

* fix: silent zero output in salary converter and NaN filter bypass in LinkedIn CLI

Bug #10 (convert_salary_excel.py):
openpyxl ws[row_index] random access fails silently under read_only=True,
leaving headers empty and producing no output. Fix: save the header row
values during the existing iter_rows scan so ws[header_row] is never called.

Bug #5 (.agents/skills/linkedin-search/cli/src/cli.ts):
parseInt on --jobage/--page/--limit flags returns NaN on non-numeric input.
NaN propagates silently — the jobage filter is dropped, page/limit are broken.
Fix: validate each parsed int, exit 1 with a structured BAD_ARG error on NaN.

Also adds:
- tests/test_bug10_salary_converter.py: 10 scenarios, 31 assertions (all green)
- tests/test_bug5_linkedin_cli.sh: 8 scenarios, 16 assertions (all green)
- docs/bugfixes.md: root cause, impact, and fix explanation for both bugs,
  plus a note on the pre-existing detect_column_type "n" pattern issue

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix: address PR review — drop salary converter change, move test to bun

- Drop tools/convert_salary_excel.py change (bug not reproducible on
  modern openpyxl; reviewer confirmed master works correctly)
- Drop tests/test_bug10_salary_converter.py and top-level tests/ dir
- Drop docs/bugfixes.md (analysis belongs in PR description, not repo)
- Replace tests/test_bug5_linkedin_cli.sh with a proper bun test file
  at .agents/skills/linkedin-search/cli/tests/cli-flag-validation.test.ts
  following the jobindex-search/cli/tests/ convention (runCLI/parseJSON
  helpers, describe/test/expect, descriptive names)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

.agents/skills/linkedin-search/cli/tests/helpers.ts

@@ -0,0 +1,39 @@
+import { join } from "path";
+
+const CLI_PATH = join(import.meta.dir, "../src/cli.ts");
+
+export interface CLIResult {
+  stdout: string;
+  stderr: string;
+  exitCode: number;
+}
+
+export async function runCLI(args: string[]): Promise<CLIResult> {
+  const proc = Bun.spawn(["bun", "run", CLI_PATH, ...args], {
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+
+  const [stdout, stderr, exitCode] = await Promise.all([
+    new Response(proc.stdout).text(),
+    new Response(proc.stderr).text(),
+    proc.exited,
+  ]);
+
+  return { stdout: stdout.trim(), stderr: stderr.trim(), exitCode };
+}
+
+export function parseJSON<T = unknown>(result: CLIResult): T {
+  if (result.exitCode !== 0) {
+    throw new Error(
+      `CLI exited with code ${result.exitCode}. stderr: ${result.stderr}`
+    );
+  }
+  try {
+    return JSON.parse(result.stdout) as T;
+  } catch {
+    throw new Error(
+      `Failed to parse JSON. stdout: ${result.stdout}\nstderr: ${result.stderr}`
+    );
+  }
+}