fix(filesystem): handle explicit read line limits

[pragnyanramtha]

Summary

• Treat head: 0 and tail: 0 as explicit read_text_file limits instead of falling through to full-file reads.
• Reject fractional line limits for head and tail at tool input validation time.
• Add MCP client integration coverage for zero, simultaneous zero, and fractional line-limit arguments.

Root Cause

readTextFileHandler used truthiness checks for optional head and tail arguments. Because 0 is falsy, a caller requesting zero lines received the complete file instead. The schema also accepted any number, so fractional values could be forwarded to line-reading helpers even though line counts should be integral.

Validation

• npm run build -w src/filesystem
• npm exec -w src/filesystem -- vitest run __tests__/structured-content.test.ts
• npm test -w src/filesystem

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[BossChaos]

Code Review

PR: fix(filesystem): handle explicit read line limits by @pragnyanramtha

• ✅ Bug/security fix

Wallet: 0xdaE5d307339074A24F579dB48e7c639359D94904

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