fix(simulator): implement missing CLI commands and align help/completer

[moralpriest]

Description

The simulator CLI had significant command-surface drift: many commands listed in help had no dispatch handler, and the three independent surfaces (dispatch switch cases, usage() help text, readline completer) had diverged.

This PR implements 11 missing command handlers and synchronizes all three surfaces so every listed command works.

Changes by commit:

1. feat(simulator): add diff and print_height handlers — Implements diff (shows current network difficulty) and print_height (shows current chain height).

2. feat(simulator): add print_bc handler for topo range output — Implements print_bc to display block info for a topo-height range, matching daemon behavior. Adds math/big import for difficulty display.

3. feat(simulator): add print_tx command support — Implements print_tx to look up and display transaction details by hash. Uncomments the transaction package import.

4. feat(simulator): add peer, sync, ban, and mining stub handlers — Implements peer_list, sync_info, ban, unban, bans using existing p2p functions. Adds start_mining/stop_mining stubs that return explicit "not supported in simulator" messages.

5. fix(simulator): align help and completer with command handlers — Synchronizes usage() and completer with the full set of implemented commands. Fixes swapped mempool_flush/"Flush regpool" and regpool_flush/"Flush mempool" descriptions. Fixes case-sensitive help dispatch (was line == "help", now uses command == "help" which goes through strings.ToLower()).

6. fix(simulator): improve unknown command guidance — Unknown commands now print "unknown command: X, try 'help'" instead of silently falling through.

NOTE: This PR targets community-dev rather than dev as this is the active development branch for community contributions.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• This will require a HardFork to be enabled

Which part is impacted ?

• Wallet
• Daemon
• Miner
• Explorer
• Simulator
• Misc (documentation, comments, text...)

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings

License

I am contributing & releasing the code under DERO Research License (which can be found here).

[8lecramm]

Good. I see no issues with the "core" functions such as "diff", "print_bc" and so on.
Do we really need p2p and mining commands? It has no use in simulator mode.

[moralpriest]

I think it would preferable to get ride of them instead of printing "command is not supported in simulator" unless there's value to have parity with the daemon. I fail to see that.