P0: Explicit save & durable persistence for the decompiler CLI

[mahaloz]

What & why

Work done through DecLib (renames, retypes, comments) could disappear after stop + reload — IDA closed its database with close_database(False), discarding everything. This is the P0 persistence gap. This PR adds a first-class, cross-backend save so agents can produce durable .i64 / Ghidra-project / .bndb artifacts.

New capabilities

• decompiler save [--path] — flush the backend's analysis to disk.
• decompiler stop --save | --discard — persist before shutdown, or explicitly drop unsaved edits (mutually exclusive).
• DecompilerInterface.save() + persist_on_close control, implemented per backend:

  Backend	Behavior
  IDA	idc.save_database; reopens an existing .i64/.idb directly on reload (no re-analysis, no headless overwrite-prompt hang)
  Ghidra	GhidraProject.save(program); teardown honors persist_on_close so --discard truly reverts
  Binary Ninja	writes/snapshots a .bndb (best-effort)
  angr	in-memory → NotImplementedError

• Clean "not implemented" UX: NotImplementedError now crosses the client/server wire intact and the CLI prints not implemented: … with a distinct exit code 2, so scripts can tell "unsupported on this backend" apart from a real failure.

Example

$ decompiler load ./fauxware --backend ida --project-dir ./proj
$ decompiler rename func authenticate auth_check
$ decompiler save
saved: True
path: None
$ decompiler stop --id <id>
$ decompiler load ./fauxware --backend ida --project-dir ./proj   # reopens saved .i64
$ decompiler list_functions --filter auth_check
0x664        184      auth_check          # the rename survived

$ decompiler save --backend angr
not implemented: this backend has no persistent database to save (e.g. angr is purely in-memory).
$ echo $?
2

Tests

Backend-parametrized tests/test_decompiler_cli.py:

• test_save_command_persists_rename_across_reload — save → stop → reload, rename intact (IDA + Ghidra, both pass).
• test_stop_save_persists_rename_across_reload — stop --save path (IDA + Ghidra pass).
• test_save_unsupported_on_inmemory_backend — angr save exits 2.
• test_stop_save_and_discard_are_mutually_exclusive.

Run with the declib env against IDA 9.2 (idalib), Ghidra 12.1 (pyghidra), and angr. Binary Ninja code paths are implemented but not exercised here (module not installed in the test env).

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First PR in a series closing the IDALib-parity gaps; subsequent PRs (comments, globals/signatures, typed reads, search, repair, patching, scripting) stack on this branch.

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https://claude.ai/code/session_01HfZHdprXg38re1XyKxzGg5