Rewrite procbuilder command README with comprehensive documentation

[Copilot]

The procbuilder README was incomplete with TODO placeholders and minimal flag documentation. This rewrite provides complete reference documentation for all 30+ command-line flags.

Changes

• Flag documentation: All flags organized into logical categories (architecture config, program input, HDL generation, simulation, inspection)
• Practical examples: 9 examples covering processor creation, assembly, HDL generation, and simulation workflows
• Workflow guides: Common development scenarios (new processor development, hardware implementation, program testing)
• Technical details: JSON machine file format, execution models (Von Neumann/Harvard/Hybrid), opcode optimization

Structure

Installation
├── Architecture Configuration (execution model, registers, memory, I/O)
├── Instruction Set Configuration (opcodes, optimizer)
├── Program Input (assembly, binary)
├── Machine State (load/save JSON)
├── Display & Inspection (show opcodes, disassemble, aliases)
├── Verilog Generation (processor, RAM, ROM, testbench, FPGA targets)
└── Simulation & Execution (step-by-step vs fast run modes)

Follows documentation style established in cmd/simbox/README.md and cmd/bmstack/README.md.

Original prompt

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This section details on the original issue you should resolve

<issue_title>procbuilder command readme docs. </issue_title>
<issue_description>Rewrite the Readme file of the procbuilder command in cmd/procbuilder/README.md</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes procbuilder command readme docs.  #43

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