feat(optional-skills): port Anthropic financial-services skills as optional finance bundle (#21180)

Adds 7 optional skills under optional-skills/finance/ adapted from
anthropics/financial-services (Apache-2.0):

  excel-author        — openpyxl conventions: blue/black/green cells,
                        formulas over hardcodes, named ranges, balance
                        checks, sensitivity tables. Ships recalc.py.
  pptx-author         — python-pptx for model-backed decks (pitch,
                        IC memo, earnings note) that bind every number
                        to a source workbook cell.
  dcf-model           — institutional DCF (49KB skill): projections,
                        WACC, terminal value, Bear/Base/Bull scenarios,
                        5x5 sensitivity tables. Ships validate_dcf.py.
  comps-analysis      — comparable company analysis: operating metrics,
                        multiples, statistical benchmarking.
  lbo-model           — leveraged buyout: S&U, debt schedule, cash
                        sweep, exit multiple, IRR/MOIC sensitivity.
  3-statement-model   — fully-integrated IS/BS/CF with balance-check
                        plugs. Ships references/ for formatting,
                        formulas, SEC filings.
  merger-model        — accretion/dilution analysis for M&A.

All seven are optional (not active by default). Users install via
'hermes skills install official/finance/<skill>'.

Hermesification:
- Stripped every Office JS / Office Add-in / mcp__office__*
  branch — skills assume headless openpyxl only.
- Replaced Cowork MCP data-source instructions with 'MCP first (via
  native-mcp), fall back to web_search/web_extract against SEC EDGAR
  and user-provided data'.
- Swapped Claude tool references (Bash, Read, Write, Edit, mcp__*)
  for Hermes-native equivalents and Python library calls.
- Canonical Hermes frontmatter (name/description/version/author/
  license/metadata.hermes.{tags,related_skills}).
- Descriptions tightened to 187-238 chars, trigger-first.
- Attribution preserved: author field credits 'Anthropic (adapted by
  Nous Research)', license: Apache-2.0, each SKILL.md links back to
  the upstream source directory.

Verification:
- All 7 discovered by OptionalSkillSource with source_id='official'
- Bundle fetch includes support files (scripts, references, troubleshooting)
- related_skills cross-refs all resolve within the bundle
- No Claude product / Cowork / Office JS / /mnt/skills leakage
  remains in body text (bounded mentions only in attribution blocks)

Source: https://github.com/anthropics/financial-services (Apache-2.0)

optional-skills/finance/excel-author/scripts/recalc.py

@@ -0,0 +1,88 @@
+#!/usr/bin/env python3
+"""Recalculate an .xlsx file's formulas using LibreOffice headless.
+
+Usage: python recalc.py <path.xlsx> [timeout_seconds]
+
+openpyxl writes formula strings but does not compute them. Downstream scripts
+that open the file with data_only=True get None for every formula cell until
+something has actually calculated the workbook. Excel does this on open;
+headless pipelines need LibreOffice (or similar) to do it explicitly.
+
+Exits 0 on success (workbook recomputed and resaved in place), non-zero on
+failure. Writes status JSON to stdout either way.
+"""
+
+import json
+import shutil
+import subprocess
+import sys
+import tempfile
+from pathlib import Path
+
+
+def find_libreoffice() -> str | None:
+    for cmd in ("libreoffice", "soffice"):
+        path = shutil.which(cmd)
+        if path:
+            return path
+    return None
+
+
+def recalc(xlsx_path: str, timeout: int = 60) -> dict:
+    src = Path(xlsx_path).resolve()
+    if not src.exists():
+        return {"status": "error", "error": f"File not found: {src}"}
+
+    lo = find_libreoffice()
+    if lo is None:
+        return {
+            "status": "error",
+            "error": "libreoffice not found on PATH — install it or recalc in a real Excel session",
+        }
+
+    with tempfile.TemporaryDirectory() as td:
+        try:
+            subprocess.run(
+                [
+                    lo,
+                    "--headless",
+                    "--calc",
+                    "--convert-to",
+                    "xlsx",
+                    str(src),
+                    "--outdir",
+                    td,
+                ],
+                check=True,
+                capture_output=True,
+                timeout=timeout,
+            )
+        except subprocess.TimeoutExpired:
+            return {"status": "error", "error": f"libreoffice timed out after {timeout}s"}
+        except subprocess.CalledProcessError as e:
+            return {
+                "status": "error",
+                "error": f"libreoffice exited {e.returncode}: {e.stderr.decode(errors='replace')[:500]}",
+            }
+
+        produced = Path(td) / src.name
+        if not produced.exists():
+            return {"status": "error", "error": "libreoffice did not produce output file"}
+
+        shutil.copy(produced, src)
+
+    return {"status": "success", "file": str(src)}
+
+
+def main():
+    if len(sys.argv) < 2:
+        print("Usage: python recalc.py <path.xlsx> [timeout_seconds]", file=sys.stderr)
+        sys.exit(2)
+    timeout = int(sys.argv[2]) if len(sys.argv) > 2 else 60
+    result = recalc(sys.argv[1], timeout=timeout)
+    print(json.dumps(result, indent=2))
+    sys.exit(0 if result["status"] == "success" else 1)
+
+
+if __name__ == "__main__":
+    main()