Feature proposal: Compare apps across keywords (rank matrix view)

[onlyilkr]

Problem

The dashboard currently shows keyword rank for one selected app at a time. When several apps compete in the same category, there is no way to see how they stack up side by side on a shared keyword set without manually switching between apps and mentally diffing the numbers.

Typical questions that are hard to answer today:

• On which keywords does my app lead vs. trail competitors?
• If I track keywords on App A and my teammate tracks a different set on App B, what does the unified picture look like?
• Where are the biggest rank gaps worth closing?

Proposal

Add a Compare Apps view reachable from the dashboard. The user picks N apps (2–10) and M keywords (1–100), and a matrix renders with rows = keywords, columns = apps, cells = current rank + change delta.

Key design point: ranks are already derivable from the existing aso_keywords.ordered_app_ids top-200 list, so an app's rank can be computed for any keyword it appears in even if that app has not explicitly tracked the keyword in app_keywords. This means the matrix is meaningful even when apps have different keyword lists.

No schema changes required. Two new read-only endpoints:

• GET /api/aso/compare/keywords — union of keywords tracked by the selected apps, with coverage metadata.
• POST /api/aso/compare/matrix — per-(app, keyword) rank/change data.

Why it fits this project

• Local-first, read-only — no new external API calls, no auth surface changes.
• Reuses existing primitives (Button, Input, Badge, Card), existing route factory pattern, and the same SQL idiom already used by keyword-handlers.ts (json_each(ordered_app_ids)).
• Respects current boundary ownership: no changes to keywordPipelineService or keywordWriteRepository.
• Adds 12 unit tests in cli/db/app-compare.test.ts (full suite still passes: 393 tests).

Scope (what would ship)

• Compare entry point next to the sidebar Apps heading.
• Live-updating matrix (debounced refetch on selection changes).
• Custom keyword picker with "tracked by all / any" filter and search.
• Per-column sort (keyword, popularity, any app's rank).
• Inline removal of apps/keywords from the matrix.
• Fullscreen toggle on the matrix (+ ESC to exit).
• localStorage persistence of last comparison.
• Three distinct empty-cell states: not tracked, outside top 200, not yet researched — each with tooltip + aria-label.

Explicitly out of scope for v1 (could come later based on feedback):

• Shareable URL state / named saved comparisons
• CSV or Markdown export
• Sparkline / historical trend per cell

Status

Implementation PR: #1

Everything passes locally (typecheck + 393/393 tests + build). I have opened the PR alongside this issue so the code is visible for review, but fully happy to adjust scope, API shape, or integration approach — or hold off entirely — based on your feedback.

Thanks for building this tool.