Complete config migration cleanup

Retire legacy files and migration fixtures, move runtime state out of the repository, and migrate Tree-sitter and textobjects to their Neovim 0.12-compatible main branches.

LOG.md

@@ -1,9 +1,9 @@
 # Neovim Rebuild — Decisions & Reference
 
-Authoritative notes for the Neovim migration. Use this alongside `MIGRATION_PLAN.md` and `neovim-migration-guide.md`.
+Historical migration record and ongoing architectural decision log.
 
-- Migration plan: MIGRATION_PLAN.md
-- Guide and requirements: neovim-migration-guide.md
+- Maintenance instructions: `AGENTS.md`
+- Active workflows and keymap reference: `README.md` and `:KeymapsGuide`
 
 ## Decisions Log
 
@@ -222,6 +222,10 @@ Record every decision here with a short rationale. Append new entries; do not re
 - 2026-10-28: Hardened preview scrolling after an interactive over-scroll surfaced a window-local error that did not reproduce headlessly. The temporary preview-window call is now protected, so stale-window and boundary failures are treated like native top/bottom clamping instead of reaching the command line.
 - 2026-10-28: Excluded netrw from automatic session persistence after `:mksession` serialized its generated `NetrwTreeListing` name and restored an empty explorer buffer. Before the existing exit-time save, preview windows and netrw windows are removed; a netrw-only tab is dropped, while the sole remaining netrw window is replaced with an ordinary file buffer or a blank fallback. Netrw is intentionally not rebuilt on load.
 - 2026-10-28: Changed the enhanced netrw `p` mapping into a true toggle. With no preview it opens the selected file or directory and begins live cursor updates; with an existing preview it closes that window and stops updates, matching manual `:pclose` behavior.
+- 2026-10-28: Declared the migration complete after sustained daily use of the modern Lua configuration. Interactive navigation, language tooling, native completion, Copilot, formatting, linting, and the enhanced netrw workflow are considered validated. Real SSH URI previews and use of stock netrw without this configuration remain optional portability checks, not release gates. This decision also ends the requirement to retain migration-only archives and fixtures in the live repository; their removal will be handled as a separate, explicit cleanup.
+- 2026-10-28: Replaced the migration-era `AGENTS.md` with a concise maintenance guide for the established configuration. Removed completed phase tracking, obsolete validation-workspace instructions, resolved issue notes, and the target-tree description; retained current architectural guardrails, documentation expectations, a smoke-test command, and a short history note.
+- 2026-10-28: Retired the completed migration's legacy configuration, vendored plugin archive, UltiSnips collection, validation workspaces, root test assets, superseded planning documents, and phase labels in active Lua comments. Git history now provides the historical archive. Persistent undo storage moved from the configuration repository to `stdpath('state')/undo`; the active README, architectural log, lockfile, colorscheme, spell data, and templates remain.
+- 2026-10-28: Diagnosed the Tree-sitter `TSNode:range()` failure as the known incompatibility between Neovim 0.12 and nvim-treesitter's locked legacy `master` branch. Migrated nvim-treesitter and nvim-treesitter-textobjects to their rewritten `main` branches: native Neovim highlighting and incremental selection replace the old modules, textobjects use explicit mappings, indentation uses the new plugin expression when a query exists, and autotag retains its direct supported setup. Installed the verified official Tree-sitter CLI 0.26.9 binary in `~/.local/bin` after the system package required interactive sudo and Cargo compilation required unavailable libclang. Reinstalled all configured parsers in the new site directory and removed obsolete generated parser copies from the plugin checkout. The plugin audit confirmed every plugin is current for its configured branch or release constraint; nvim-surround remains on the latest release rather than its newer unreleased `main` commit.
 
 ## Project-Local Configuration
 
@@ -263,7 +267,9 @@ Neoconf and the earlier layered JSON proposal were rejected. They remain in the
 - `listchars` and `showbreak` will reuse legacy values.
 - `autocomplete` with `completeopt = menu,menuone,noselect,popup,fuzzy` for Neovim 0.12 native completion.
 
-## Process Reminders
+## Maintenance Reminders
 
-- After any change or decision, update this README and MIGRATION_PLAN.md.
-- Keep subphases small and verify each step in isolation.
+- Follow `AGENTS.md` for current maintenance rules.
+- Update `README.md` when user-facing behavior changes.
+- Record significant architectural decisions in this log.
+- Keep changes focused and verify affected workflows.