Refresh SKILL.md for v2.1 tool surface, fix marketplace.json skills path, adopt #12's path-resolution fixes

[cdebled]

What & why

Brings SKILL.md up to date with the current MCP tool surface (search, tree, nodeDetails, findElement, extract, sessions, PandaScript replay, agent mode) and fixes several real bugs found while doing it.

Changes

• Documents all 5 interfaces (MCP, CLI fetch, CDP, agent mode, PandaScript) and the full current MCP tool/resource list — verified tool-by-tool against a live connection to the real server, and CLI flags verified against lightpanda help <command> on the latest nightly.
• Fixes .claude-plugin/marketplace.json's skills field to point at a directory instead of ./SKILL.md — closes marketplace.json: skills entry should be a directory path, not "./SKILL.md" #16.
• Adds ${CLAUDE_SKILL_DIR}-based install instructions for Claude Code, with a plain fallback for other agent runtimes, so scripts/install.sh resolves correctly when this skill runs as a plugin (cwd isn't the skill's own directory in that case).
• Resolves lightpanda via PATH lookup (bare command name) instead of hardcoding ~/.local/bin/lightpanda, including in the MCP JSON configs — drops the sh -c "exec ..." wrapper entirely, since it was only ever needed to expand $HOME, and spawn()/execvp resolve a bare command via PATH without a shell regardless (verified with a no-shell subprocess call). The hardcoded path broke for anyone who installed via Homebrew, AUR, or a .deb package rather than scripts/install.sh, which this PR also documents as alternatives. Adopts the diagnosis from fix MCP path resolution (addresses #10), CDP connection limit, Playwright signature #12 (not cherry-picked directly — this branch had diverged too far for a clean apply — see the commit for co-author credit).
• Corrects the CDP connection limit note (said 1, defaults to 16).
• De-duplicates the Playwright/Puppeteer CDP examples (was ~90% identical boilerplate).
• Points the two CLI common-options mentions at lightpanda help <command> plus the live run-locally/commands/* guide pages, and the PandaScript reference at the existing live usage page, instead of linking to docs pages that only exist in an unmerged docs-repo PR.
• Drops the frontmatter's OpenClaw-specific claim ("drop-in replacement for Chrome and OpenClaw default browser") in favor of a generic one — there's no unique integration to justify naming one agent over the others this skill also supports (Claude Code, opencode, Cursor, Codex CLI, ...).
• Uses "Lightpanda" as SKILL.md's author, matching marketplace.json's existing convention of crediting the company rather than an individual.
• Bumps plugin version to 2.1.0 to match SKILL.md's metadata version.

Notes for reviewers

• Supersedes Fix Claude Code plugin #10 (its two fixes are already covered here and via merged expand $HOME automatically #15).
• Overlaps fix MCP path resolution (addresses #10), CDP connection limit, Playwright signature #12 — recommend closing it once this merges, its two real fixes are folded in here with credit.
• Does not touch scripts/install.sh — unbreak macOS Apple Silicon install, atomic Linux install, real version smoke test #11 (Apple Silicon AMFI fix, atomic install) is independent and worth merging on its own; testing today reproduced its SIGKILL bug live on Apple Silicon, which is a point in favor of prioritizing it.
• Does not include default --block-private-networks for agent-driven examples (SSRF defense) #13's security section — separate scope.

[arrufat]

Thanks for the thorough refresh — I verified most of this against the browser source and a live MCP connection, and the surface documentation all checks out: the 31-tool MCP list matches the live server exactly, the new fetch/serve flags and defaults match Config.zig, the --port/--cdp-port exclusivity and its rationale match main.zig, the LP domain additions exist, and the ${CLAUDE_SKILL_DIR} / skills: ["./"] / frontmatter changes match the Claude Code docs. The marketplace and PATH-resolution fixes are good to land.

Two factual issues to fix before merge, and one structural point worth discussing — all inline below.

[cdebled]

Thanks for the thorough review, @arrufat. Addressed all five points. Replies with the specifics are on each of your inline comments. Pushed in 76ff891 and 7ed6209.

Specifically, I vendored the browser repo's generated pandascript skill as a second skill: skills: ["./", "./pandascript"]. Trimmed the hand-written PandaScript section to how to produce and replay a script.

Two open items in the vendored pandascript skill, not blocking this PR. Both need a fix upstream in skill.zig, not patched here, since a hand fix would get overwritten on the next refresh:

• It says Run with: ./lightpanda agent script.js instead of the newer lightpanda run script.js.
• Its .goto line claims a timeout does NOT reject. Per Runtime.zig's settlePending, it does reject, with "navigation timed out". Same claim repeats in the best practices section.

[arrufat]

Wasn't that addressed here already?
lightpanda-io/browser@78f24b5

[cdebled]

Wasn't that addressed here already? lightpanda-io/browser@78f24b5

Ah yes, my bad, missed that.