feat(cli): try confirm-or-revert prefs

[benallfree]

Summary

Draft for visibility. Adds try [reboot] <secs> <set-args>: apply a pref trial, persist it like set, and auto-revert on RTC timeout unless the same key is committed with set. Up to 4 concurrent slots in /try.json (survives reboot). Optional reboot reverts then reboots; set radio / set freq inherit reboot-on-revert.

Upstream CommonCLI + role loop() hooks only. No board variants, slim builds, or EnvyOS-specific radio/FEM work in this PR.

Prior art / related

• tempradio (mainline): temporary RF 4-tuple, live apply, not saved to prefs. #1910 (parser hardening only).
• hop.ignore (#2980): volatile RAM test knob, not persisted.

try covers any set-able pref (plus powersaving on|off): trial persisted, revert snapshot in /try.json, RTC timer, commit via matching set.

Sample commands

try 3600 radio.rxgain off
try reboot 3600 radio.rxgain off
try 3600 radio 915.0,250,11,5
try 1800 powersaving on
get try
set radio.rxgain off
get radio.rxgain

try 10 radio.rxgain off
get try
# wait ~10s
get radio.rxgain
get try

Test plan

• USB: try 10 radio.rxgain off → get try → wait → reverts
• Reboot mid-trial: prefs + /try.json reload; timer still active
• try then set same key commits and clears slot
• try 3600 radio … reboot armed on revert
• Denied keys rejected; fifth slot returns Error: try slots full

[LitBomb]

@benallfree are you the guy behind envybot?

https://www.reddit.com/r/meshcore/comments/1w5whrh/a_local_5013c_organization_is_vibe_coding_a/

https://github.com/MeshEnvy/envybot