perf: cache size and jump_target from first pass in to_bytecode

[P403n1x87]

ConcreteBytecode.to_bytecode makes two passes over the instruction list. The first pass (finding jump targets) already calls c_instr.get_jump_target(offset) and c_instr.size for every instruction. The main loop then called both again — redundantly, at the same offsets.

This change stashes (size, jump_target) per instruction into a list during the first pass and consumes it via an iterator in the main loop, eliminating all second calls to get_jump_target and size.

Profiling data

Hotspot	Before	After
ConcreteBytecode.to_bytecode own	9.56%	8.29%
ConcreteBytecode.to_bytecode total	19.55%	15.55%
ConcreteInstr.get_jump_target total	2.74%	gone (< top 20)
ConcreteInstr.size total	1.30%	gone (< top 20)

Benchmark runs

	Range	Avg
Before	214–226 r/s	~221 r/s
After	224–232 r/s	~229 r/s

~3.5% throughput improvement.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.40%. Comparing base (e5d1d74) to head (fa35a70).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #200   +/-   ##
=======================================
  Coverage   95.39%   95.40%           
=======================================
  Files           7        7           
  Lines        2107     2110    +3     
  Branches      456      456           
=======================================
+ Hits         2010     2013    +3     
  Misses         54       54           
  Partials       43       43           

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