Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@CHANGELOG.rst`:
- Line 4: The changelog entry only documents the new update notice for the
"dfetch check" command but omits the "dfetch environment" command; update the
CHANGELOG.rst entry to mention both commands and clarify their differing
behavior — state that "dfetch check" shows a dim notice below the header and is
skipped in CI environments, while the "dfetch environment" command (implemented
in dfetch.commands.environment) shows the notice unconditionally — keep the
wording concise and consistent with the existing bullet style.

In `@dfetch/commands/check.py`:
- Around line 102-108: The log interpolates raw GitHub tag text from
newer_version_available() into a Rich-formatted message (variable newer) which
could be interpreted as Rich markup; fix by escaping the value before
interpolation (use rich.markup.escape or equivalent) and log escape(newer) in
the logger.info call where newer is used so the message uses a safe, literal
version string.

In `@dfetch/commands/environment.py`:
- Around line 39-45: The Rich-formatted log interpolates the GitHub-derived
variable newer directly (see newer_version_available() and the logger.info
call), so escape the string before formatting to avoid accidental Rich markup
injection: import rich.markup.escape (or equivalent) and use escape(newer) in
the f-string passed to logger.info (e.g., f"[dim]  dfetch {escape(newer)}
available — https://github.com/dfetch-org/dfetch/releases[/dim]"); no other code
paths need changing.

In `@tests/test_github_version_check.py`:
- Around line 23-71: Add three unit tests to tests/test_github_version_check.py
to cover the edge cases where the GitHub JSON response has (1) no "tag_name"
key, (2) an empty "tag_name" value (""), and (3) a non-string "tag_name" (e.g.
integer or null). For each new test (e.g. names like
test_newer_version_missing_tag_name_returns_none,
test_newer_version_empty_tag_name_returns_none,
test_newer_version_non_string_tag_name_returns_none) patch
dfetch.util.github_version_check.urllib.request.urlopen, return a mock response
whose read() yields the appropriate JSON bytes ({"some_other_key": "x"},
{"tag_name": ""}, {"tag_name": 123} or {"tag_name": null}), and assert that
newer_version_available() returns None; reuse the existing pattern of
context-manager mock setup used in other tests.

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Duplicate comments:
In `@CHANGELOG.rst`:
- Line 4: The changelog entry for issue `#1262` in CHANGELOG.rst line 4 is too
generic and doesn't accurately reflect the different behavior between the two
commands. Reword the bullet point to clarify that dfetch check skips the version
notice during CI environments, while dfetch environment consistently displays
the notice regardless of the CI context. This will make the release note more
precise and informative about the actual user-visible behavior differences.

In `@dfetch/util/github_version_check.py`:
- Around line 41-42: The except clause in the version check function that
catches URLError, JSONDecodeError, and ValueError lacks a comment explaining the
intentional exception suppression. Add a comment above or within the except
block (before the pass statement) that clearly documents that these exceptions
are intentionally being ignored because the version check is a best-effort
operation and failures should not impact the main application functionality.