feat(shell): enhance log browser, add yay wrapper, and integrate starship OSC prompt markers

- logs.fish: add yay category, ov-powered viewing for paru/yay (section
  headers, color highlights, ==> AUR build markers) and scrollback logs
  (OSC 133;A sticky prompt headers); add fzf Ctrl-D delete with Y/n
  confirm and list refresh, ? toggleable help overlay; run
  _scrollback_prune_junk before building file list
- _scrollback_prune_junk: new utility to remove empty, single-line, and
  Kitty tab-rename noise logs before display and before max-file pruning;
  called from both logs and smart_exit
- smart_exit: call _scrollback_prune_junk before counting toward max files
- conf.d/yay-wrapper.fish: auto-generate ~/.local/bin/yay logging wrapper
  mirroring paru-wrapper; tees output to timestamped logs, prunes old ones
- conf.d/starship.fish: move fish_prompt from config.fish; emit OSC 133;A
  after the prompt's leading newline so the marker lands on the info-bar
  line rather than the blank line above it; guard with type -q starship so
  clean fish sessions use built-in markers unchanged
- config.fish: remove inline fish_prompt block (now in conf.d/starship.fish);
  add return sentinel at EOF to prevent tool-injected init lines from running
- completions/ov.fish: add ov tab completions
- README.md: document all of the above

config.fish

@@ -172,12 +172,6 @@ if status is-interactive
     #   Helps ensure that Claude Code's terminal output is clean and doesn't have flickering issues.
     set -gx CLAUDE_CODE_NO_FLICKER 1
 
-    #   ─────────────────────────── Starship prompt ────────────────────────────
-    #   Initializes the Starship prompt, which provides a highly customizable and informative command prompt.
-    #   This is wrapped in a check to ensure that it only runs if Starship is installed,
-    #   preventing errors if it's not available.
-    type -q starship; and starship init fish | source
-
     #   ╭────────────────────────────── OVERRIDES ─────────────────────────────╮
     #   |       Run these last so they can override any previous settings.     |
     #   |    This is useful for machine-specific behavior or configurations.   |
@@ -204,3 +198,8 @@ if status is-interactive
     #    |                        End of override section.                     |
     #    ╰──────────────────────────── END OVERRIDES ──────────────────────────╯
 end
+
+# Tools like starship, zoxide, etc. append init lines below this point via their
+# setup commands. We manage all integrations through conf.d/ instead, so we
+# return here to prevent injected lines from conflicting with that setup.
+return