docs: one accounting guide instead of nine

There were nine accounting documents, each covering part of the picture and
pointing at the others for the rest — so no one file answered a question end to
end. They are now one: docs/الدليل-المحاسبي-الكامل.md, 1,607 lines, self-contained,
with no reference to any sibling guide.

Merged in full, nothing dropped:

  - معالج توزيع المبالغ — the five scopes, stage skipping, member-category
    precedence, the running remainder, the mandatory remainder line, the
    resulting-entry panel, versioning on save, and all 17 rejection cases
  - أنواع البنود for both collection and disbursement, and why a stamp fee
    booked as revenue overstates profit and misstates the tax base
  - الضرائب — inclusive vs added vs exempt vs zero-rated, and why exempt blocks
    input-tax recovery while zero-rated does not
  - مسار الفلوس — the four chains, the FIFO ageing behind «فين الفلوس دلوقتي»,
    and the treasury reclassification with its three guarantees
  - الاستحقاقات — including the point the whole thing turns on: collection posts
    revenue directly, so an accrual left standing books the income twice
  - سد الفجوات, the three-way purchase match, the cheque lifecycle through
    bounce and re-presentation, vouchers, chart-of-accounts management
  - the fixed-asset cycle, reclassification, payroll, inventory, closing,
    reports, the 39-tool index, troubleshooting, and the open decisions

Verified: 26 diagrams parse against the real mermaid parser, all 59 routes it
cites resolve against the router, all 37 table-of-contents anchors resolve, and
a 29-topic coverage check against the replaced files comes back clean. The nine
originals remain in git history.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>