fix(install): relink Dreamcoder over ML4W and onboard Herdr 0.9.1

[Dreamcoder08]

Summary

dreamcoder install|repair stowed modules that were renamed to Dreamcoder* long ago, and ML4W upgrades re-point fish, kitty and fastfetch at their own tree. This slice restores the stow layer and adds the installed Herdr version.

Changes

• Stow module list matches the Dreamcoder* packages (test pins it to installer_plan())
• Foreign symlinks and conflicting files are moved, never deleted, to ~/.local/share/dreamcoder/install-conflicts/<id>/ before stowing
• Herdr 0.9.1 profile, generated variants and verifier support; dev-dots uses the 0.9.1 CLI
• Fish autostart launches Herdr with SHELL pinned to fish

Verification

tests/shell/test_stow_layer.bats, Herdr contract/generation tests and the full suites green; stow -n -v of all modules into an empty HOME is conflict-free; herdr config check ok for the generated variants.

Chain Context

Field	Value
Chain	ML4W 2.16 + Herdr 0.9.1 + Light/Dark-only stabilisation
Tracker PR	Not needed (stacked PRs to main)
Position	2 of 6
Base	pr/01-ml4w-2.16-compat
Depends on	#11
Follow-up	#13
Review budget	621 / 400
Starts at	the tip of pr/01-ml4w-2.16-compat
Ends with	fix(install): relink Dreamcoder over ML4W and onboard Herdr 0.9.1

Chain Overview

main
 └── #11 fix(ml4w)
  └── 📍 #12 fix(install)
   └── #13 fix(theme)
    └── #14 fix(shell)
     └── #15 refactor(theme)
      └── #16 chore(quality)

Scope

• Includes: see Changes above
• Excludes:
• Theme mode and colour stability (PR 3)

Autonomy

• CI is expected to pass for this PR branch
• This PR has one deliverable scope
• This PR can be rolled back without unrelated changes
• Tests, docs, or manual verification cover this unit

[Dreamcoder08]

Verified independently at this slice tip (stacked PRs do not run CI until retargeted to main): pytest exit 0, ruff clean, bats 1 failure. The single bats failure is apply-theme-mode.sh kanagawa bridge carries night-derived colors, which already fails on main; it is removed together with Night in #15 (bats 0 failures there).