Add feature documentation generation skill

.claude/skills/generate-feature-docs/SKILL.md

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+---
+name: generate-feature-docs
+description: Generate feature documentation under user-docs/<featureName>, auto-detecting whether the feature is backend/frontend/full-stack, auto-capturing screenshots when missing, and auto-linking related existing docs.
+argument-hint: "[featureName]"
+allowed-tools: Read, Write, Edit, Glob, Grep, Bash, Skill
+---
+
+Generate documentation for feature `$1`.
+
+## Step 1 — Classify the feature (backend / frontend / full-stack)
+
+Before touching screenshots, search the repository for files relevant to `$1` (by feature name, route/URL fragments, and obvious keyword variants — kebab-case, camelCase, PascalCase). Use Glob/Grep across the whole repo, not just `user-docs/`.
+
+Bucket what you find:
+
+- **Backend evidence**: controllers/route handlers, services, repositories/DAOs, models/entities, DTOs, API/OpenAPI specs, migrations.
+- **Frontend evidence**: templates/views, components (`.tsx`/`.jsx`/`.vue`/`.svelte`/etc.), client-side JS/TS driving the feature, feature-specific CSS.
+
+Classify as:
+
+- **Backend-only** — backend evidence found, no dedicated frontend surface for this feature.
+- **Frontend-only** — frontend evidence found, no dedicated backend/API code for this feature (e.g. it's purely client-side, or it consumes a generic existing endpoint).
+- **Full-stack** — both.
+
+This classification drives the structure of both output docs (see Step 3) and whether screenshot capture is even applicable (Step 2).
+
+## Step 2 — Screenshots
+
+Screenshots live in:
+
+`${CLAUDE_PROJECT_DIR}/user-docs/$1/screenshots`
+
+The directory may contain screenshot1.png, screenshot2.png, ... screenshotN.png — never assume a fixed count. If it already exists and has image files, use those as-is; do not move, rename, or modify them, and skip straight to Step 3.
+
+If it's missing or empty:
+
+- **Backend-only feature**: there is nothing to screenshot. Don't attempt capture and don't treat this as an error — proceed to Step 3 and produce an API-usage guide instead of a screenshot walkthrough.
+- **Frontend-only or full-stack feature**: attempt to auto-capture screenshots before giving up:
+  1. Check whether a `run` skill is available for this project (or a documented dev-server command in README/CLAUDE.md/package.json). Use it to start the app locally.
+  2. Use the claude-in-chrome tools to navigate to the page(s)/route(s) identified in Step 1, drive the feature through its main states (e.g. initial view, an interactive/opened state, a filled-in or filtered state), and capture one screenshot per meaningful state.
+  3. Save each capture into `${CLAUDE_PROJECT_DIR}/user-docs/$1/screenshots/` as `screenshot1.png`, `screenshot2.png`, etc., in the order a user would encounter them.
+  4. If the app can't be started, the relevant route can't be found, or browser automation isn't available, stop capture attempts — don't fabricate what the UI looks like from code alone.
+
+  If auto-capture wasn't possible, stop and report this clearly to the user instead of guessing at the feature's UI. Suggest checking for a typo in the feature name, confirming the app can run locally, or adding screenshots manually.
+
+## Step 3 — Generate the docs
+
+Inside `${CLAUDE_PROJECT_DIR}/user-docs/$1/` folder create exactly:
+
+1. `implementation-details.md`
+2. `user-guide.md`
+
+### implementation-details.md
+
+- State the feature's classification (Backend-only / Frontend-only / Full-stack) up top with a one-line rationale (what evidence led to it).
+- Explain what the feature does.
+- Explain its main workflow — end-to-end for full-stack (UI → API → service → data), request/response-centric for backend-only, or UI/state-centric for frontend-only.
+- Find all files in the repository that are relevant to this feature and list them with a brief description of their purpose.
+- Analyze code style, patterns, and conventions used in the relevant files.
+- Explain any relevant implementation details that can be inferred from the repository code.
+- If backend-only (or full-stack with a non-trivial API surface), include an **API Reference** section: endpoints, HTTP methods, request/response shapes, inferred from the controller/route and DTO code — not invented.
+- Add a link to the detailed guide:
+
+  `[See the user guide](./user-guide.md)`
+
+### user-guide.md
+
+- **Frontend-only / full-stack, with screenshots**: provide step-by-step instructions based on the screenshots (existing or freshly captured in Step 2). Use all relevant screenshots, but don't force every screenshot into the document if one is redundant.
+- **Backend-only (no UI, no screenshots)**: provide a usage guide instead — example requests (curl or equivalent) and example responses for each relevant endpoint, derived from the controller/DTO code.
+- Add a link back to the implementation details:
+
+  `[For more info, check out implementation-details](./implementation-details.md)`
+
+When embedding screenshots, calculate the correct relative path from the generated Markdown file to the original screenshot.
+
+Do not invent UI behavior that cannot be inferred from the screenshots or repository code.
+
+## Step 4 — Auto-link related documentation
+
+Look for existing documentation that overlaps with this feature:
+
+- Other folders under `user-docs/*/` whose `implementation-details.md` references any of the same files you listed in Step 1 (shared controller, service, model, component, etc.), or whose feature name/keywords clearly overlap.
+- Repo-level docs (`README.md`, `CLAUDE.md`, `docs/**`) that mention this feature or the same relevant files.
+
+If you find genuine overlap (shared files or explicit textual reference — not a guessed/topical relationship), add a **Related Documentation** section near the end of `implementation-details.md` listing each with a relative link and a one-line reason (e.g. "shares `ExportService` with the CSV export feature"). Skip the section entirely if nothing genuinely overlaps — don't invent relationships.
+
+Only edit the files you are generating in `user-docs/$1/`. Do not modify other features' existing docs to add backlinks.