add dolibarr-thirdparty-completeness and dolibarr-tva-deductible

V4 bundle — two more sibling skills, both read-only, both depending
on the dolibarr base skill.

dolibarr-thirdparty-completeness:
- audit-thirdparty.sh <socid>: country-aware completeness audit for
  any thirdparty (FR: SIREN + SIRET + tva_intra; EU non-FR: tva_intra;
  extra-EU: national tax id). Generalizes the V1 KM-hardcoded script.
- audit-all-thirdparties.sh: loops over /thirdparties and surfaces a
  compact table of gaps. --clients-only / --suppliers-only flags.
- Live baseline finds 5/10 thirdparties with mandatory gaps:
  KissMetrics (US tax id), Wise Europe SA (BE tva_intra), Medialex
  (FR SIRET + tva_intra), Qonto (SIRET), Infogreffe (SIRET).

dolibarr-tva-deductible:
- deductible-by-month.sh: TVA déductible aggregated per period × rate.
- deductible-line-detail.sh: per supplier-invoice line with country-
  based CA3 bucket assignment (ligne 20 for 20 % FR, ligne 19 for
  reduced rates, ligne 17+24 for intra-UE autoliquidation).
- Live baseline: 223.22 € total TVA déductible across 13 lines.
  Wise Europe SA correctly identified as intra-UE autoliquidation;
  La Poste correctly identified as FR exempt (timbres).
- Mirrors dolibarr-tva-reconciliation on the supplier side. Together
  they give the two numbers a CA3 monthly declaration needs.

Also extends dolibarr/SKILL.md endpoint catalogue with /supplierinvoices
(noting the 403 on the /lines sub-endpoint — inline lines on the detail
endpoint make this a non-issue). dolibarr/README.md gains two new
permission checkboxes for Factures fournisseurs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.claude/skills/dolibarr-tva-deductible/examples/deductible-by-month.txt

@@ -0,0 +1,16 @@
+# TVA déductible by month × rate — window=-inf → +inf
+
+month      tva_tx  count      basis HT     TVA ded  CA3 line
+------------------------------------------------------------------------------
+2025-10   20.0000      2          6.08        1.22  ligne 20
+2026-01    0.0000      2         58.43        0.00  ligne 17 + 24 (autoliquidation) — verify with line-detail
+2026-01   20.0000      8        345.02       69.00  ligne 20
+2026-02   20.0000      2        765.00      153.00  ligne 20
+------------------------------------------------------------------------------
+           TOTAL                      1174.53      223.22
+
+# Notes:
+#   - This is TVA déductible (supplier side). For TVA collectée (customer side),
+#     use dolibarr-tva-reconciliation/scripts/tva-by-month.sh.
+#   - tva_tx==0 lines may be either truly exempt (e.g. La Poste timbres)
+#     or autoliquidation intra-UE (e.g. Wise). Run deductible-line-detail.sh.