Add positional helpers to maps library (CELLDIST, ADDRESSES, ROW/COL helpers)

[jimmytacks]

Summary

Six small Maps lambdas covering the address ↔ position conversion graph and grid distance:

• CELLDIST(cell1, cell2, [metric]) — Manhattan (0, default), Chebyshev (1), or Euclidean (2) distance between two A1 addresses. Pure-arithmetic body so Excel broadcasting handles both same-shape zip and column × row cartesian inputs naturally.
• ADDRESSES(cells) — range reference → A1 strings, shape-preserving. Closes the gap where downstream lambdas want string addresses but the caller has a reference.
• ROWOF / COLOF — extract row/col from a CELLTOPOS-encoded position, with optional [mult] matching the CELLTOPOS / POSTOCELL convention.
• ROWNUM / COLNUM — row/col from A1 address text, like ROW() / COLUMN() but accepting strings. Composed on top of CELLTOPOS so address-parsing edge cases (sheet prefix, $, ranges, case-insensitive, multi-letter cols up to XFD) are inherited.

Together with the existing CELLTOPOS / POSTOCELL, this completes the three-way conversion graph between A1 text, (row, col), and encoded position.

Closes #182
Closes #183
Closes #185

Test plan

• Format validation: 424 tests pass
• Harness functional tests: all 452 tests pass (includes new ROWOF/COLOF/ROWNUM/COLNUM/ADDRESSES/CELLDIST coverage with scalar, array-lift, sheet-prefix, $-anchor, cell-reference, and cartesian-broadcast cases)
• Spot-check in Excel: try =CELLDIST("F28", "G26") → 3, =CELLDIST({"A1";"B2"}, {"C3","D4"}) → 2×2 grid, =ADDRESSES(F28:H30) → 3×3 of strings, =ROWNUM("AA17") → 17, =COLNUM("XFD1") → 16384

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