Fix zsh post-prompt input hitch

[shunk031]

Summary

• remove the duplicate mise activate zsh call from .zprofile
• keep mise hook registration and path/env setup synchronous so fresh interactive zsh sessions are input-ready as soon as the prompt appears
• defer only the noncritical zsh plugins that can safely load later, while keeping zsh-syntax-highlighting and zsh-autopair eager for stable prompt-ready behavior
• document in the sheldon config why zsh-syntax-highlighting and zsh-autopair stay eager while zsh-autosuggestions and zsh-completions remain deferred, group the eager plugins directly under that rationale for readability, and add small per-plugin notes for the eager entries

Testing

• git diff --check
• chezmoi execute-template --file home/dot_config/exact_sheldon/plugins.toml.tmpl
• PTY probe with temporary ZDOTDIR/XDG_CONFIG_HOME to verify both prompt -> 150ms input and prompt -> 1.2s input stay responsive with and without TMUX

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.69%. Comparing base (e19b803) to head (756c9b8).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #427      +/-   ##
==========================================
+ Coverage   89.11%   89.69%   +0.58%     
==========================================
  Files           9        9              
  Lines         248      233      -15     
==========================================
- Hits          221      209      -12     
+ Misses         27       24       -3     

Flag	Coverage Δ
macos-14-client	41.66% <ø> (ø)
ubuntu-latest-client	89.27% <ø> (+0.96%)	⬆️
ubuntu-latest-server	87.93% <ø> (-1.14%)	⬇️

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