fix: resolve all P1/P2 security and crash issues (#6–#33)

[Copilot]

Summary

This PR fixes all 25 P1/P2 issues found in the issue tracker, covering shell injection, path traversal, XSS, authentication, memory safety, crash/panic scenarios, and logic bugs.

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Changes

🔴 P1 Security

Issue	File	Fix
#33/#19	android/device.rs	Shell-quote every adb argument with POSIX single-quote wrapping to prevent metacharacter injection
#32	handlers/system.rs	Cap HTTP scrape response body at 10 MB; reject oversized content-length early
#31	platform/macos/ax.rs	Replace get_unchecked() on CFArray with safe .get() to prevent UB on inconsistent AX API lengths
#28	android/input.rs	Escape \n and \r in adb input text — they were treated as command terminators by the device shell
#27	android/input.rs	Validate press_key argument against KEYCODE_[A-Z0-9_]+ allowlist
#26	android/navigation.rs	Validate launch_app package name against [a-zA-Z0-9._] to prevent shell injection
#25	main/index.ts	Validate tabId with /^[\w-]+$/ before using it in file paths; validation moved to top of handler
#24	main/index.ts	Restrict coworkerFetchUrl local file reads to within the user's home directory
#23	Settings/shared.tsx	Configure marked renderer to strip raw HTML blocks, preventing XSS via dangerouslySetInnerHTML
#7	main.rs + nativecore-service.ts + computer-use.ts	Generate a cryptographically-random 64-char bearer token at startup; enforce Authorization: Bearer <token> on every HTTP MCP request; thread token through all MCP config injection paths

🔴 P1 Crash / Safety

Issue	File	Fix
#30	handlers/system.rs	Return an error when HOME is unset instead of silently resolving ~/x as /x
#29	hover_tracker.rs, screen_recorder.rs	Replace .unwrap() on Mutex::lock() with .unwrap_or_else(|e| e.into_inner()) to avoid cascading panics on mutex poison
#10	parent_watch.rs	Exit the process on thread spawn failure instead of silently ignoring — prevents orphaned processes

🔴 P1 Correctness

Issue	File	Fix
#9	handlers/system.rs	Use -KILL/-TERM flag for pkill; -s is a session-ID filter, not a signal selector
#8	singleton.rs	Acquire flock(LOCK_EX) around the read-kill-write critical section to eliminate the TOCTOU race

🟡 P2

Issue	File	Fix
#18	gateway/adapter.ts	Replace unbounded Map with BoundedMap(100) — evicts least-recently-inserted entries above limit
#17	nativecore-service.ts	Replace proc.stdout! non-null assertion with explicit null guard and early rejection
#16	find_image.rs	Return 0.0 when denominator is zero or non-finite in NCC, rather than propagating NaN
#15	gateway/bridge/input.ts	Map any role that is not 'assistant' to 'user' to prevent Anthropic API 400 errors
#14	cron.ts	Clamp setTimeout delay to 2^31 - 1 ms (≈24.8 days); reschedule without firing when capped
#13	handlers/system.rs	Use tasklist /FO CSV /NH on Windows instead of Unix-only ps -axo
#12	handlers/system.rs	Canonicalize the search root path via std::fs::canonicalize to prevent find ../../etc traversal
#11	handlers/system.rs	Check cp exit status and return an error when it fails
#6	find_image.rs	Guard search_region boundaries against u32 underflow before performing ss_w - r.x

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Test Results

• Rust: 80/81 tests pass; the 1 failure (test_execute_command_osascript) is pre-existing (macOS-only test, Linux CI environment lacks osascript)
• TypeScript: 413/414 tests pass; the 1 failure (injectOpencodeMcpUrl) is pre-existing (XDG_CONFIG_HOME set in CI overrides the test's home parameter)
• No new test failures introduced by these changes