refactor(registry): convert to nested TOML sections format

[jdx]

Summary

• Converted registry.toml from flat format (tools.name.field = value) to nested sections format ([tools.name])
• Added JSON schema for registry validation
• Added taplo configuration for TOML formatting

Test plan

• Build passes with new format
• mise registry output matches the previous format
• mise run lint:toml passes
• Tool resolution still works (mise ls-remote bob)

Details

The registry now uses proper TOML sections which is more standard and easier to read/edit. For example:

Before:

[tools]
bob.description = "A version manager for neovim"
bob.backends = ["aqua:MordechaiHadad/bob", "ubi:MordechaiHadad/bob[matching_regex=bob-(linux|macos|windows)-(arm|x86_64)\\.zip$]", "cargo:bob-nvim"]
bob.test = ["bob --version", "bob-nvim {{version}}"]

After:

[tools.bob]
description = "A version manager for neovim"
backends = [
    "aqua:MordechaiHadad/bob",
    "ubi:MordechaiHadad/bob[matching_regex=bob-(linux|macos|windows)-(arm|x86_64)\\.zip$]",
    "cargo:bob-nvim"
]
test = [
    "bob --version",
    "bob-nvim {{version}}"
]

🤖 Generated with Claude Code

[Copilot]

Pull Request Overview

This PR refactors the registry format from flat TOML structure to nested sections, improves error handling for NPM backend dependency checking, and adds validation/formatting infrastructure for the registry.

• Converted registry.toml from flat format to nested TOML sections format
• Added comprehensive error checking for npm/bun availability in NPM backend operations
• Added JSON schema validation and TOML formatting configuration for registry management

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

File	Description
src/backend/npm.rs	Added dependency checking for npm/bun with helpful error messages
schema/mise-registry.json	Added JSON schema for registry validation
e2e/backend/test_npm_missing_error	Added end-to-end test for npm missing error scenarios
.taplo.toml	Added TOML formatting configuration

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[github-actions]

Hyperfine Performance

mise x -- echo

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.14 x -- echo	20.3 ± 0.4	19.1	22.9	1.00
mise x -- echo	20.8 ± 0.3	20.0	22.5	1.02 ± 0.03

mise env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.14 env	19.9 ± 0.4	19.2	26.6	1.00
mise env	20.4 ± 0.4	19.5	22.9	1.03 ± 0.03

mise hook-env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.14 hook-env	19.6 ± 0.8	19.0	33.3	1.00
mise hook-env	19.9 ± 0.4	19.1	21.1	1.01 ± 0.04

mise ls

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.14 ls	17.4 ± 0.7	16.8	24.8	1.00
mise ls	17.7 ± 0.4	17.0	20.9	1.02 ± 0.05

xtasks/test/perf

Command	mise-2025.9.14	mise	Variance
install (cached)	174ms	✅ 105ms	+65%
ls (cached)	66ms	65ms	+1%
bin-paths (cached)	76ms	71ms	+7%
task-ls (cached)	474ms	471ms	+0%

✅ Performance improvement: install cached is 65%