Cleanup: post-merge follow-ups from PR #87 (upstream v0.13.0 sync)

[satwareAG-ironMike]

Follow-up cleanup items spotted during review of #87 (merge 5ddf6a3, upstream v0.13.0 sync). Both are non-blocking; filing as one issue since they are tiny and share the same origin.

1. _require_https should reuse the hostname local

File: src/specify_cli/commands/bundle/__init__.py:829

After the ValueError guard was added, the final host-check re-accesses parsed.hostname instead of reusing the hostname local captured in the try block:

try:
    parsed = urlparse(url)
    hostname = parsed.hostname
except ValueError:
    raise BundlerError(...) from None
is_localhost = hostname in ("localhost", "127.0.0.1", "::1")
...
if not parsed.hostname:                       # <- should be `not hostname`
    raise BundlerError(f"Refusing to download {label} from URL with no host: {url}")

Not a bug (ParseResult is immutable for a given URL, so a successful first access won't raise on re-access), but inconsistent with the sibling fix in src/specify_cli/presets/__init__.py:2093, which uses the hostname local consistently. Mirror that pattern here to prevent drift in future refactors.

Fix: one-line change - if not parsed.hostname: -> if not hostname:.

2. Markdown blank lines in new extensions section

File: docs/reference/extensions.md

The new "Project Extension and Hook Configuration" section runs paragraphs directly into closing code fences and table rows:

• Line 180-181: closing ``` immediately followed by paragraph text
• Line 227-228: closing table row immediately followed by paragraph text

Most renderers tolerate this, but CommonMark may treat the run-together text as a block continuation in some cases. Add a blank line in both spots.

Acceptance

• src/specify_cli/commands/bundle/__init__.py:829 uses hostname local
• docs/reference/extensions.md has blank lines after the closing fence (line 180) and after the hook-fields table (line 227)
• Existing bundle tests still pass: uv sync --extra test && .venv/bin/python -m pytest tests/commands/bundle/ tests/test_workflows.py -q

Context

• Originated from: Integrate upstream github/spec-kit v0.13.0 (#86) #87 (closes upstream-sync: v0.13.0 available #86)
• Upstream tag: github/spec-kit v0.13.0
• Both items noted as non-blocking in the PR Integrate upstream github/spec-kit v0.13.0 (#86) #87 review