fix(cli): default capture output to ./capture/ (auto-suffix capture-2/, capture-3/ on re-run)

`hyperframes capture <url>` (no -o) used to dump into `./captures/<hostname>/`,
which buries the project two levels deep and silently merges re-runs into the
previous dir — file-by-file, so leftover screenshots / assets from the prior
run stay mixed in and any later `glob` sees both.

Switch the default to `./capture/`. When it already exists, auto-suffix to
`./capture-2/`, `./capture-3/`, … (up to -99). Each capture is its own clean
directory — no crud, no friction, no clobber. The CLI prints a one-line note
when the suffix kicks in so the user sees which dir actually got written.
Explicit `-o <name>` is unaffected (still overwrite-tolerant).

skills/website-to-video/references/step-0-capture.md

@@ -20,7 +20,7 @@ Example: `npx hyperframes capture https://stripe.com -o videos/stripe-launch/cap
 
 Keeping capture artifacts (`screenshots/`, `assets/`, `extracted/`, `AGENTS.md`, `CLAUDE.md`) in a dedicated `capture/` subfolder keeps them isolated from later build files (`SCRIPT.md`, `STORYBOARD.md`, `DESIGN.md`, `compositions/`, `index.html`, `narration.wav`, `transcript.json`, `renders/`, `snapshots/`), which all live at `<project-dir>/` root.
 
-For exploratory captures that aren't becoming a video yet, `-o captures/<name>` at the repo root is fine — the isolation convention only matters when you're building a video on top of the capture.
+For exploratory captures that aren't becoming a video yet, the default `./capture/` (or any `-o <name>` you pick) is fine — the isolation convention only matters when you're building a video on top of the capture.
 
 ## Confirm it succeeded