fix(examples/chrome-applescript): use JSON.stringify for AppleScript string interpolation

[bryan-anthropic]

Summary

Follow-up to #230. Replaces escapeForAppleScript() with JSON.stringify() at the two remaining AppleScript string-interpolation sites in examples/chrome-applescript: the url param in open_url and the code param in execute_javascript (via wrappedCode).

escapeForAppleScript only handled backslash, double quote, \n, and \r — tab, null, and other control characters passed through unescaped. JSON.stringify produces an RFC 8259–compliant quoted string that AppleScript parses as a string literal, covering the gaps.

Also adds new URL(url) validation to open_url so malformed URLs return isError: true instead of reaching osascript.

With those call sites migrated, escapeForAppleScript has no remaining callers and is deleted.

Fix

• open_url: "${escapeForAppleScript(url)}" → ${JSON.stringify(url)} (+ new URL(url) validity check before building the script)
• execute_javascript: "${escapeForAppleScript(wrappedCode)}" → ${JSON.stringify(wrappedCode)} at both interpolation sites
• Delete unused escapeForAppleScript helper
• tab_id sanitization is unchanged (landed in fix(examples/chrome-applescript): sanitize tab_id to prevent AppleScript injection #230)

Test plan

• node --check examples/chrome-applescript/server/index.js
• yarn install && yarn lint clean
• grep -n escapeForAppleScript examples/chrome-applescript/server/index.js → no matches
• Manual: open_url with url: "https://example.com/a\"b" → navigates to example.com/a%22b; the " is percent-encoded as a literal URL character, not an osascript escape
• Manual: execute_javascript with a code string containing ", \t, and \\ → characters preserved as-is in the returned value
• Manual: open_url with url: "not a url" → isError: true, Invalid URL

Note for reviewers: testing execute_javascript requires Chrome's View → Developer → Allow JavaScript from Apple Events toggle to be enabled. Without it, the call to execute t javascript fails and is surfaced as a generic "Chrome not running" error via the existing outer try/catch. Not a change in this PR — documenting the prerequisite.

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[tobinsouth]

Security review

Verdict: ✅ Safe — fix is complete and correct.

Reviewed for: JSON.stringify → AppleScript breakout potential, regression vs the deleted escapeForAppleScript, new URL() validation scope, and completeness of interpolation-site coverage.

JSON.stringify safety — AppleScript string literals terminate only on an unescaped ". JSON.stringify guarantees " → \\" and \\ → \\\\, so no raw terminator or stray escape can reach the closing quote. The non-AppleScript escapes JSON emits (\\b, \\f, \\uXXXX) and raw U+2028/U+2029 contain no " — worst case is mis-rendering or a script parse error, never breakout. Inputs are type-guarded as strings before stringify (the existing typeof url !== "string" check; wrappedCode is a template literal), so output is always the "..." form. No injection path.

Regression vs old escaper — None. The deleted helper already covered \\ and " (the only breakout-relevant characters); JSON.stringify covers those plus \\t and all C0 control chars. Strictly ≥ old coverage.

new URL() validation — Permits javascript: / file: / data:, but the prior code had no validation at all and the server already exposes execute_javascript, so no new capability is granted. Defense-in-depth only.

Completeness — escapeForAppleScript fully removed. Remaining AppleScript interpolations are: safeTabId (sanitized in #230), JSON.stringify(url) (L296-297), JSON.stringify(wrappedCode) (L656/666), the hardcoded jsCode constant (L727/737), and operation.tabScript / successMessage (all callers pass literal constants). No user-input site left uncovered.

CI green across CodeQL + full test matrix. Approving.