docs(offline): add v0.6.0 deprecation notice with rationale

- Help text: note bundled assets become default in v0.6.0
- Docstring: explain why GitHub download is being retired (no network
  dependency, no proxy/firewall issues, guaranteed version match)
- Runtime nudge: when bundled assets are available but user takes the
  GitHub download path, suggest --offline with rationale
- docs/installation.md: add deprecation notice with full rationale

Author: mnriem

docs/installation.md

@@ -119,6 +119,8 @@ specify init my-project --ai claude --offline
 
 The `--offline` flag tells the CLI to use the templates, commands, and scripts bundled inside the wheel instead of downloading from GitHub.
 
+> **Deprecation notice:** Starting with v0.6.0, `specify init` will use bundled assets by default and the `--offline` flag will be removed. The GitHub download path will be retired because bundled assets eliminate the need for network access, avoid proxy/firewall issues, and guarantee that templates always match the installed CLI version. No action will be needed — `specify init` will simply work without network access out of the box.
+
 > **Note:** Python 3.11+ is required.
 
 > **Windows note:** Offline scaffolding requires PowerShell 7+ (`pwsh`), not Windows PowerShell 5.x (`powershell.exe`). Install from https://aka.ms/powershell.

src/specify_cli/__init__.py

@@ -1710,7 +1710,7 @@ def init(
     debug: bool = typer.Option(False, "--debug", help="Show verbose diagnostic output for network and extraction failures"),
     github_token: str = typer.Option(None, "--github-token", help="GitHub token to use for API requests (or set GH_TOKEN or GITHUB_TOKEN environment variable)"),
     ai_skills: bool = typer.Option(False, "--ai-skills", help="Install Prompt.MD templates as agent skills (requires --ai)"),
-    offline: bool = typer.Option(False, "--offline", help="Use assets bundled in the specify-cli package instead of downloading from GitHub (no network access required)"),
+    offline: bool = typer.Option(False, "--offline", help="Use assets bundled in the specify-cli package instead of downloading from GitHub (no network access required). Bundled assets will become the default in v0.6.0 and this flag will be removed."),
     preset: str = typer.Option(None, "--preset", help="Install a preset during initialization (by preset ID)"),
     branch_numbering: str = typer.Option(None, "--branch-numbering", help="Branch numbering strategy: 'sequential' (001, 002, ...) or 'timestamp' (YYYYMMDD-HHMMSS)"),
 ):
@@ -1722,6 +1722,12 @@ def init(
     package instead (no internet access required, ideal for air-gapped or
     enterprise environments).
 
+    NOTE: Starting with v0.6.0, bundled assets will be used by default and
+    the --offline flag will be removed. The GitHub download path will be
+    retired because bundled assets eliminate the need for network access,
+    avoid proxy/firewall issues, and guarantee that templates always match
+    the installed CLI version.
+
     This command will:
     1. Check that required tools are installed (git is optional)
     2. Let you choose your AI assistant
@@ -1934,6 +1940,14 @@ def init(
 
     use_github = not (offline and _core is not None)
 
+    if use_github and _core is not None:
+        console.print(
+            "[yellow]Note:[/yellow] Bundled assets are available in this install. "
+            "Use [bold]--offline[/bold] to skip the GitHub download — faster, "
+            "no network required, and guaranteed version match.\n"
+            "This will become the default in v0.6.0."
+        )
+
     if use_github:
         for key, label in [
             ("fetch", "Fetch latest release"),