docs: update cache-behavior with env_cache information

[jdx]

Summary

• Documents the env_cache setting in the cache-behavior docs
• Removes outdated advice to "submit a ticket" for dynamic exec-env scripts
• Explains how env plugins can declare themselves cacheable
• Shows how to opt out of caching with cacheable = false
• Clarifies in env-plugin-development.md that users must enable env_cache = true for plugin caching to work

This addresses user questions about caching for dynamic environment providers like secret managers (see discussion #3712).

🤖 Generated with Claude Code

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Note

Adds comprehensive docs for environment caching and clarifies exec-env caching expectations.

• Introduces Environment Caching section in cache-behavior.md, documenting settings.env_cache, env_cache_ttl, automatic invalidation triggers, and directive-level opt-out via cacheable = false
• Documents how env plugins (vfox modules) declare cacheability via MiseEnv returning { cacheable = true, watch_files = [...] }, with pointers to plugin docs
• Adds tips/notes in env-plugin-development.md that caching requires env_cache = true
• Removes outdated guidance about submitting tickets for dynamic exec-env scripts

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[Copilot]

Pull request overview

This PR documents the env_cache feature for managing environment variable caching in mise, particularly for dynamic environment providers. It removes outdated troubleshooting advice and provides clear configuration examples.

Changes:

• Added comprehensive documentation for the env_cache setting and its TTL configuration
• Documented cache invalidation triggers and plugin cacheability options
• Removed outdated advice to submit tickets for dynamic exec-env scripts

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[github-actions]

Hyperfine Performance

mise x -- echo

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.1.8 x -- echo	19.5 ± 0.3	18.9	21.6	1.00
mise x -- echo	19.8 ± 0.4	19.1	23.6	1.01 ± 0.02

mise env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.1.8 env	19.1 ± 0.6	18.1	21.5	1.00
mise env	20.2 ± 0.9	18.7	26.7	1.06 ± 0.06

mise hook-env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.1.8 hook-env	19.4 ± 0.6	18.6	21.7	1.00
mise hook-env	20.0 ± 0.8	18.9	23.2	1.03 ± 0.05

mise ls

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.1.8 ls	17.4 ± 0.6	16.5	20.0	1.00
mise ls	17.8 ± 0.7	16.8	20.8	1.03 ± 0.06

xtasks/test/perf

Command	mise-2026.1.8	mise	Variance
install (cached)	109ms	110ms	+0%
ls (cached)	66ms	66ms	+0%
bin-paths (cached)	70ms	70ms	+0%
task-ls (cached)	282ms	308ms	-8%