Stage 4: TOML integrations — gemini and tabnine migrated to plugin architecture (#2050)

Add TomlIntegration base class in base.py that mirrors MarkdownIntegration:
- Overrides command_filename() for .toml extension
- Extracts description from YAML frontmatter for top-level TOML key
- Renders prompt body in TOML multiline basic strings with escaped backslashes
- Keeps full processed template (including frontmatter) as prompt body
- Byte-for-byte parity with v0.4.4 release ZIP output

Create integrations/gemini/ and integrations/tabnine/ subpackages:
- Config-only __init__.py subclassing TomlIntegration
- Integration-specific update-context scripts (sh + ps1)

Add TomlIntegrationTests mixin with TOML-specific validations:
- Valid TOML parsing, description/prompt keys, {{args}} placeholder
- Setup/teardown, manifest tracking, install/uninstall round-trips
- CLI auto-promote (--ai) and --integration flag tests
- Complete file inventory tests (sh + ps)

Register both in INTEGRATION_REGISTRY; --ai auto-promote works automatically.

src/specify_cli/integrations/gemini/__init__.py

@@ -0,0 +1,21 @@
+"""Gemini CLI integration."""
+
+from ..base import TomlIntegration
+
+
+class GeminiIntegration(TomlIntegration):
+    key = "gemini"
+    config = {
+        "name": "Gemini CLI",
+        "folder": ".gemini/",
+        "commands_subdir": "commands",
+        "install_url": "https://github.com/google-gemini/gemini-cli",
+        "requires_cli": True,
+    }
+    registrar_config = {
+        "dir": ".gemini/commands",
+        "format": "toml",
+        "args": "{{args}}",
+        "extension": ".toml",
+    }
+    context_file = "GEMINI.md"

src/specify_cli/integrations/gemini/scripts/update-context.ps1

@@ -0,0 +1,23 @@
+# update-context.ps1 — Gemini CLI integration: create/update GEMINI.md
+#
+# Thin wrapper that delegates to the shared update-agent-context script.
+# Activated in Stage 7 when the shared script uses integration.json dispatch.
+#
+# Until then, this delegates to the shared script as a subprocess.
+
+$ErrorActionPreference = 'Stop'
+
+# Derive repo root from script location (walks up to find .specify/)
+$scriptDir = Split-Path -Parent $MyInvocation.MyCommand.Definition
+$repoRoot = try { git rev-parse --show-toplevel 2>$null } catch { $null }
+# If git did not return a repo root, or the git root does not contain .specify,
+# fall back to walking up from the script directory to find the initialized project root.
+if (-not $repoRoot -or -not (Test-Path (Join-Path $repoRoot '.specify'))) {
+    $repoRoot = $scriptDir
+    $fsRoot = [System.IO.Path]::GetPathRoot($repoRoot)
+    while ($repoRoot -and $repoRoot -ne $fsRoot -and -not (Test-Path (Join-Path $repoRoot '.specify'))) {
+        $repoRoot = Split-Path -Parent $repoRoot
+    }
+}
+
+& "$repoRoot/.specify/scripts/powershell/update-agent-context.ps1" -AgentType gemini

src/specify_cli/integrations/gemini/scripts/update-context.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# update-context.sh — Gemini CLI integration: create/update GEMINI.md
+#
+# Thin wrapper that delegates to the shared update-agent-context script.
+# Activated in Stage 7 when the shared script uses integration.json dispatch.
+#
+# Until then, this delegates to the shared script as a subprocess.
+
+set -euo pipefail
+
+# Derive repo root from script location (walks up to find .specify/)
+_script_dir="$(cd "$(dirname "$0")" && pwd)"
+_root="$_script_dir"
+while [ "$_root" != "/" ] && [ ! -d "$_root/.specify" ]; do _root="$(dirname "$_root")"; done
+if [ -z "${REPO_ROOT:-}" ]; then
+  if [ -d "$_root/.specify" ]; then
+    REPO_ROOT="$_root"
+  else
+    git_root="$(git rev-parse --show-toplevel 2>/dev/null || true)"
+    if [ -n "$git_root" ] && [ -d "$git_root/.specify" ]; then
+      REPO_ROOT="$git_root"
+    else
+      REPO_ROOT="$_root"
+    fi
+  fi
+fi
+
+exec "$REPO_ROOT/.specify/scripts/bash/update-agent-context.sh" gemini