docs: add GDB debugging evidence path

[div0rce]

Summary

Adds a repeatable GDB debugging evidence path and bounds existing debugger transcripts. This change is software-only and does not add new hardware evidence.

Changes

• Added GDB setup, breakpoint, variable-inspection, and limitation notes.
• Added a debugger session command template and observations placeholder.
• Linked existing transcripts as bounded historical artifacts in the evidence map.

Validation Tasks

• git status --short --branch
• git diff --check
• platformio test -e native
• scripts/check_app_core_includes.sh
• Claim-safety grep contains only explicit non-claim boundary wording

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Replace nonexistent symbol in GDB session template

The new command file includes print/x some_state_variable, but that symbol does not exist in the firmware sources (it only appears in this template), so users following this “repeatable evidence path” will hit a debugger error at that step and won’t get a usable variable-inspection example from the provided script. Use a real symbol (for example from AppCoreContext or fault state) or clearly mark this line as a placeholder with instructions to edit before use.

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