Validate graph invariants during deserialization

[isPANN]

Summary

• Share private construction checks with deserialization for SimpleGraph, DirectedGraph, BipartiteGraph, MixedGraph, and PlanarGraph.
• Return deserialization errors for out-of-range endpoints, overflowing bipartite vertex counts, and violations of the existing planar edge-count bound.
• Keep public constructor signatures and serialized formats unchanged. PlanarGraph still checks only its documented necessary edge-count condition, not full planarity.
• Ten files; based directly on main.

Verification

• Five regression tests fail on main: ordinary graph decoding panics, while the other graph types accept invalid data.
• Full workspace all-feature tests: 6,483 passed; 2 existing ignored.
• Topology coverage run: 116 passed; changed-line coverage 100% across 146 lines.
• Workspace all-target all-feature Clippy with warnings denied, formatting, and diff whitespace checks passed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.93%. Comparing base (7dd5fcd) to head (7e4f62f).

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #1159    +/-   ##
========================================
  Coverage   95.93%   95.93%            
========================================
  Files        1074     1074            
  Lines      132106   132224   +118     
========================================
+ Hits       126730   126849   +119     
+ Misses       5376     5375     -1     

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[isPANN]

Consolidated into #1161 as graph and set-system input validation. Combined workspace all-feature tests and Clippy pass.