feat: expose TabsVim_* public functions, remove all OOTB keybindings

[jesse23]

Summary

• Removes all hard-coded keybindings from the plugin; only mouse drag-and-drop (bracketed-paste infrastructure) remains OOTB
• Promotes 6 logic-heavy operations to a stable public TabsVim_* function API: ToggleHorizTerm, ToggleVertTerm, NewTabTerm, CloseOrHide, RenameBuffer, FzfOpenInTab
• Simple native commands (:tabnew, :sp, :tabonly, etc.) are documented as direct vimrc mappings — no wrapper exposed
• Adds ADR-004 and new key-binding SPEC documenting the public API, recommended vimrc wiring, and trade-off notes for g<number> and <C-]>

Test plan

• Verify TabsVim_ToggleHorizTerm / TabsVim_ToggleVertTerm toggle persistent split terminals
• Verify TabsVim_NewTabTerm opens terminal in a new tab with nobuflisted
• Verify TabsVim_CloseOrHide prompts on last window, hides terminal, closes normal split
• Verify TabsVim_RenameBuffer prompts and renames buffer
• Verify TabsVim_FzfOpenInTab opens fzf with tabedit sink (requires fzf.vim)
• Verify mouse drag-and-drop still opens files in new tab
• Verify no stray keybindings are installed by the plugin

[Copilot]

Pull request overview

This PR refactors tabs.vim to stop installing user keymaps by default and instead exposes a small public TabsVim_* function API, with new documentation (SPEC + ADR) describing recommended user-side vimrc mappings and the rationale for removing hard-coded bindings.

Changes:

• Removed all user-facing OOTB keybindings from plugin/tabs.vim and promoted several script-local operations to public TabsVim_* functions.
• Added a new key-binding SPEC documenting the public API and suggested vimrc wiring patterns.
• Added ADR-004 documenting the decision/trade-offs for keybinding cleanup.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 9 comments.

File	Description
plugin/tabs.vim	Removes hard-coded mappings and exposes public TabsVim_* functions for terminal/window/buffer operations and fzf integration.
docs/specs/key-binding.md	New SPEC describing “no OOTB keybindings” posture, public function API, and recommended vimrc mappings.
docs/adrs/004.tabs-vim.keybinding-cleanup.md	New ADR explaining why keybindings were removed and why a public function API is the preferred contract.

Comments suppressed due to low confidence (1)

plugin/tabs.vim:80

• TabsVim_CloseOrHide() uses winnr('$') == 1 to decide whether to prompt and qall!. winnr('$') is per tab page, so this will incorrectly prompt to quit when closing the only window in a tab even if other tabs exist. Consider checking both tabpagenr('$') == 1 and winnr('$') == 1 (or an equivalent “last tab + last window” condition) before prompting/qall!, and otherwise just close the window/tab normally.

function! TabsVim_CloseOrHide() abort
  if winnr('$') == 1
    if confirm('Quit Vim?', "&Yes\n&No", 2) == 1
      qall!
    endif
    return
  endif

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[jesse23]

Addressed all Copilot review comments in 770f02b:

plugin/tabs.vim:107 — TabsVim_FzfOpenInTab: added guard for exists('*fzf#vim#files') and exists('*fzf#vim#with_preview'); shows a clear WarningMsg and returns early if fzf.vim is not available.

plugin/tabs.vim:77 — TabsVim_CloseOrHide: untracked terminal buffers (e.g. tab terminals from TabsVim_NewTabTerm) now fall back to plain close instead of incorrectly toggling a split terminal. Only bufnrs matching s:term_bufnr or s:vterm_bufnr are toggle-hidden.

plugin/tabs.vim:80 (suppressed) — TabsVim_CloseOrHide: quit prompt now checks tabpagenr('$') == 1 && winnr('$') == 1 so closing the last window in a tab with other tabs open no longer prompts to quit Vim.

docs/specs/key-binding.md:21 — Rephrased to "no user-facing keybindings"; clarified that <F30>/<F31> are internal DnD aliases, not user-facing mappings.

docs/specs/key-binding.md:129 — Features table updated to ✅ since this PR implements all three items.

docs/adrs/004:55 — Updated docs/specs/tabs.vim.md to add a reference to key-binding.md in the Related Specs section, fulfilling what the ADR claimed.

docs/specs/key-binding.md:35,43,49 / docs/adrs/004:45 — The || table || comments appear to be false positives. The tables use standard GFM format (| col | col |) with correct separator rows. They render correctly on GitHub.