Speed up fish prompt and mise activation

[djensenius]

Summary

This PR is a performance pass over interactive shell/tmux startup paths. It keeps the existing workflows and visual setup, but removes repeated work from prompt rendering, mise activation, tmux window labels, tmuxinator startup, and tmux plugin startup.

Performance results

Area	Before	After	Savings	Change
Starship right prompt	~0.9-1.2s	~19-21ms	~0.9-1.2s per prompt	Custom jj modules run with sh instead of Fish and skip work outside .jj repos.
Fish startup	noticeably slower from duplicate mise activation	~0.10s	avoided duplicate activation	Disabled Homebrew's vendor mise activate fish with MISE_FISH_AUTO_ACTIVATE=0.
Mise hook on Enter	ran on every prompt	no prompt hook	avoids repeated prompt work	Replaced default prompt hook with startup activation plus a PWD change hook.
Mise PWD env refresh	repeated prompt-time work	~8-10ms only on directory changes	prompt stays fast	mise hook-env -s fish runs only when PWD changes.
Mise remote/tool resolution	repeated GitHub/version lookups and rate-limit warnings	cached for 1h	avoids repeated network/version checks	Enabled mise env/version caches and used gh auth token for GitHub API auth.
Starship custom jj modules	Fish startup for each custom module	shell + .jj guard	right prompt down to ~20ms	Uses cheap guard before calling jj.
Tmux contextual window label helper	~70-100ms per common pane label	~10-20ms	~50-90ms per label render	Added shell fast path for common fish/nvim panes; Python fallback remains.
Tmux status refresh	helpers ran every 1s	every 5s	fewer recurring helper processes	Raised status-interval from 1 to 5.
pt / personal tmux session launcher	~7.6-7.7s via tmuxinator	~3.2s cold before async TPM	~4.4s	Replaced only pt with a direct Fish function that creates the same personal session layout.
Tmux cold startup	~2.1-2.3s	~0.02-0.03s immediate return	~2.1s	TPM now loads asynchronously in the background.
pt after async TPM	~3.2s cold path	~0.03s immediate return	~3.1s	Direct pt launcher benefits from async TPM.

Key findings

Finding	Evidence	Resolution
Tmux itself was not slow	Minimal tmux startup measured ~20-30ms. Full config measured ~2.1-2.3s.	Focused on TPM/plugin loading rather than tmux core.
TPM was the cold-start bottleneck	Removing only the TPM runner dropped startup to ~30ms.	Moved TPM into a background loader.
Missing npm@latest made mise noisy/slow	Mise tried GitHub npm/cli release lookups and hit rate limits when npm was missing.	Kept npm = 'latest' after installing it locally and added caching/auth.
Starship right prompt was dominated by custom shell modules	jj custom modules were running through Fish and costing close to a second.	Switched custom module shell to sh and added .jj guards.
tmuxinator start personal was much slower than equivalent tmux commands	tmuxinator start personal --no-attach measured ~7.6-7.7s; direct equivalent was much faster.	Added a dedicated pt Fish function for the personal session only.

Files changed by area

Area	Files	Purpose
Mise caching/auth	mise/config.toml	Cache remote version/env data for 1h and authenticate GitHub requests via gh auth token.
Fish/mise activation	fish/conf.d/00-env.fish, fish/config.fish	Disable duplicate Homebrew mise auto-activation and run mise env refresh on startup/PWD change only.
Prompt speed	starship.toml	Make custom jj prompt modules cheaper.
Tmux status/window labels	tmux/tmux.conf, scripts/tmux-contextual-window-name-fast.sh, scripts/tmux-show-outdated.sh	Reduce recurring status work and speed common contextual window labels.
Personal tmux launcher	fish/conf.d/21-aliases.fish, fish/functions/pt.fish	Replace pt tmuxinator alias with a direct session launcher.
Async TPM	tmux/tmux.conf, scripts/tmux-load-plugins.sh	Load plugins in the background and show loading/failure status.
Misc user changes included	bat/config, fish/completions/copilot.fish	Bat theme naming and Copilot completion update.

Tmux async loading details

Tmux startup was split into two phases:

Phase	Behavior
Immediate startup	Tmux creates the server/session and becomes usable in ~20-30ms.
Background plugin load	scripts/tmux-load-plugins.sh runs TPM, then reapplies post-tpm.conf, status-style, mouse/mode settings, and post-catppuccin.conf.
Status indicator	loading plugins appears in yellow while loading; it clears on success and shows plugin load failed in red on failure.
Settle time	Plugin keybinds/theme/status settled after roughly 2 seconds in testing.

Tradeoffs

Tradeoff	Impact
Async TPM is eventually consistent	Plugin-provided keybinds and final theme/status styling may not be available for the first second or two after a brand-new tmux server starts.
pt no longer uses tmuxinator	Only the personal session hot path changed. gt and st still use tmuxinator.
Status helpers refresh less often	Package/speedtest/battery-style status updates can lag by up to 5s, but this avoids rerunning helpers every second.
Mise caches for 1h	Newly released remote tool versions may not appear immediately, but prompt/startup avoids repeated remote checks.

Commits

Commit	Description
9630301	Speed up fish prompt and mise activation
9c216b6	Update bat theme and copilot completions
aa4642a	Reduce tmux status line overhead
8d84613	Restore contextual tmux window labels
12b41ce	Add fast path for tmux window labels
69fb038	Speed up personal tmux session launcher
fd32d1f	Load tmux plugins asynchronously