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 `@backend/app/services/intelligence/github_link_service.py`:
- Around line 130-133: The code incorrectly treats an empty calendars list as a
fetch failure; change the logic so cache.warning_message is set only on an
actual fetch error (e.g., exception or explicit failure result) rather than when
calendars is falsy. Update the call site (where fetch_all_contribution_calendars
is invoked and cache.warning_message is set) to inspect a success flag or catch
exceptions from fetch_all_contribution_calendars (or change
fetch_all_contribution_calendars to return a (success, calendars) result) and
only call get_error("github_link.contribution_fetch_failed") when the fetch
failed, not when calendars == [] while token exists; keep existing variables
like token, calendars, cache.warning_message and the get_error call to locate
and implement the change.

In `@backend/tests/test_github_link.py`:
- Around line 157-168: The test test_only_language_topic_description_sources is
vacuous because it asserts sources <= {"language","topic","description"} and
would pass if extract_skills returned no skills; change the assertion to require
the exact set of sources produced by the fixture (e.g., assert sources ==
{"language","topic","description"}) and optionally assert result.skills is
non-empty to ensure the three source paths in extract_skills are actually
exercised.

In `@frontend/src/components/forms/CareerDiffModal.tsx`:
- Around line 91-92: The current row key built from path + kind collides when
buildReviewEntries(changes) yields multiple changes for the same path; update
the key used when rendering reviewEntries to include a unique identifier per
change (for example append the change's id/uid or the item's index in the
grouped array) instead of only path+kind so duplicate-path modified entries get
distinct keys; search for usages of reviewEntries and the key expression
(formerly `${path}-${kind}`) in the component (also update the similar key at
the other occurrence referenced around the second spot) and replace it with
something like `${path}-${kind}-${change.id || idx}` to ensure stable, unique
keys.

---

Outside diff comments:
In `@backend/tests/test_github_collector_extended.py`:
- Around line 128-142: The helper _mock_collect currently forces a non-empty
languages payload by using "languages or {'Python': 10000}", which prevents
tests from simulating an empty language response; change the patch for
fetch_languages in _mock_collect to pass languages if it is not None, and only
use the default {"Python": 10000} when languages is exactly None (e.g., use a
conditional expression like languages if languages is not None else {"Python":
10000}), so callers can pass {} to simulate no-language responses while existing
callers that omit languages keep the default.

In `@frontend/src/components/forms/CareerDiffModal.tsx`:
- Around line 99-115: scrollToPath currently only queries elements by data-fp
and misses the injected removal stubs from injectRemovedPlaceholders; update
scrollToPath (using editedFrameRef and the escaped fp) to first look for the
removal stub selector created by injectRemovedPlaceholders (for example a stub
attribute or marker like a data-fp-removed / data-removed attribute combined
with the exact fp), then fall back to the existing queries (`[data-fp="..."]`
and `[data-fp^="..."]`) so clicks target the injected stub for removed array
items instead of the reindexed next item.

---

Nitpick comments:
In `@frontend/src/components/github-link/ContributionHeatmap.tsx`:
- Line 59: The JSX currently embeds literal year-based labels (e.g., in
ContributionHeatmap.tsx at the div with className styles.statLabel and the ARIA
text on the other line) which violates the SSoT message rule; replace these
literals with calls to the frontend message constants (compose a parameterized
message like contributionYear or contributionYearAria in your messages/SSoT
module) and pass calendar.year as the parameter, then import and use those
message constants in ContributionHeatmap.tsx to render both the visible label
and the ARIA text.

In `@frontend/src/components/github-link/GitHubLinkDashboard.tsx`:
- Around line 106-129: The JSX in GitHubLinkDashboard uses inline user-facing
strings ("Activity", the select aria-label "表示する年", and the option label suffix
"年") — move these to the centralized message SSoT constants and reference them
instead; update the component to import the message keys (e.g., ACTIVITY_LABEL,
YEAR_SELECT_ARIA, YEAR_SUFFIX) and replace the literals in the h2, select
aria-label, and option display (currently inside the map over
result.contribution_calendars) while leaving behavior tied to selectedYear,
setSelectedYear, and the active calendar logic unchanged.