Unify the development environment and manage CLI tools with mise

[jiminu]

Summary

• Replace selectable minimal/developer profiles with one development environment declared in packages.conf.
• Remove --profile, profile-selection state, and profile-specific configuration branches. Keep a simple completed-configuration marker.
• Manage Starship, fzf, zoxide, ripgrep, eza, bat, and jq through mise on both macOS and Ubuntu; preserve eza/bat as optional.
• Pin Starship to 1.26.0 in config/shared/mise.toml, remove its direct-download/Homebrew installation paths, and use the shared mise version-update workflow.
• Update release payloads, lifecycle tests, documentation, and the isolated full-mode benchmark for the unified environment.
• Query installed mise versions for status/doctor, excluding orphaned shims; isolate installer-owned mise operations from the caller's project configuration.
• Pin fzf/zoxide in the full benchmark and assert real shell integration startup. Extend Ubuntu E2E with conflicting project pins, Zsh startup, and configured-but-uninstalled Starship checks.

Intentional compatibility change

Profile selection and legacy profile migration are deliberately not retained. This is a single-environment product change, not an automatic migration of old minimal installations. Existing user configuration and installed tools are not deleted as part of this PR.

Verification

• Local WSL: PATH="<pinned-neovim-bin>:$PATH" bash scripts/check.sh (21 test suites, syntax, ShellCheck, and formatting).
• Real isolated installation: SELFISHELL_BENCHMARK_ITERATIONS=3 PATH=/usr/bin:/bin bash scripts/benchmark.sh --mode full provisions pinned mise/Zinit and mise-managed Starship/fzf/zoxide; their resolved paths and Zsh initialization are checked before timing.
• Empty temporary HOME with real mise: uninstalled Starship reports missing; a conflicting Node 24.13.0 project no longer overrides the release's 24.18.0 installer selection.
• Isolated WSL comparison with identical Starship 1.26.0 binaries: login/non-login first prompts initialize correctly; warmed first prompt medians were 35.72 ms direct vs. 37.54 ms via mise (50 samples), prompt rendering 2.31 ms vs. 2.32 ms (100 samples).
• GitHub Actions run 34855452692 passed for c183fd0: Linux/macOS shell checks, the expanded Ubuntu 24.04 real installation lifecycle, macOS configuration lifecycle, and pinned Neovim E2E. GitGuardian also passed.
• Follow-up review identified and prompted fixes for installed-version detection and project-config interference; regression tests cover both.
• Independent review of those fixes found no further actionable issues.
• Fixed the previous macOS test failure by replacing GNU-specific sed basic-regex alternation with portable extended-regex syntax; the new macOS gate passed.

Scope retained

• OS foundation packages stay with Apt/Homebrew; Zsh and Neovim plugins stay with their existing managers.
• No Mason/LSP or development/CI-tool migration is included.
• No merge, tag, or release publication is part of this change.