Add keep_focus_on_list: stay on the list when selecting a channel or opening a thread

[Frodotus]

Closes #83.

What

A new [general] bool, keep_focus_on_list (default false). When enabled, selecting a channel or opening a thread loads the content but leaves keyboard focus on the list, so you can browse with j/k + Enter without tabbing back each time.

[general]
keep_focus_on_list = true

Behavior (when true)

Selecting still loads the content; only the focus jump is suppressed:

• sidebar → channel: focus stays on the sidebar
• channel message → its thread: thread opens, focus stays on the message list
• threads view → thread: thread opens, focus stays on the threads list

Step into the content via the existing focus keys (Tab / l / →). Default (false) is the long-standing focus-follows-selection behavior, so nobody is affected unless they opt in.

Implementation

• Gates the three selection-driven focusedPanel assignments — reduceChannelSelected (channel pick), handleEnter (threads-view Enter), and openThreadPanel (message → thread) — behind !a.keepFocusOnList.
• Wires config.General.KeepFocusOnList → app.SetKeepFocusOnList(...), mirroring the other [general]/[appearance] bools.
• Intentionally not gated: ThreadsViewActivatedMsg still focuses the threads list — that list is what you browse in the threads view, so landing on it is the on-list behavior (commented inline). Mouse click-to-focus-a-pane is also untouched.

Tests

Three tests, each driving a real production path and asserting default-vs-flag:

• channel select via the ChannelSelectedMsg reducer (Update)
• message → thread via the real handleEnter keystroke
• threads view → thread via the real handleEnter keystroke

Full suite + go vet green. Wiki Configuration.md updated ("Browsing without losing focus").

[gammons]

hi @Frodotus curious why you're closing your PRs!

[Frodotus]

hi @Frodotus curious why you're closing your PRs!

Hi! Sorry for the confusion — no slight intended! I opened those while trying to get slk working as my daily driver, but I'm not really a Go person. In the end I built my own client in Python since it's what I know — that way I can quickly tweak things to fit my daily-driver needs instead of it turning into a Go learning project. Really appreciate slk though, and the effort you've put into it!