docs(limitations): add explicit boundaries guide based on #117 feedback

[naffee]

Description

This PR adds the explicit boundaries and limitations guide (LIMITATIONS.md) requested in the issue to build buyer trust.

It specifically incorporates the structural feedback provided by @stevesagronegocios673-ux that was approved by the maintainers:

• Included a plain-English "buyer-trust" opening statement.
• Added a "Current Status Overview" table mapping capabilities to live/roadmap states.
• Explicitly defined the 5 boundaries (Compliance, Evidence, Tool-Governance, Isolation, Deployment) in honest, under-claimed language.
• Added high-visibility links to the document at the top of the README.md and in the docs index.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• make check passes (tests + lint + vet) (N/A - Docs only)
• Contribution guidelines in CONTRIBUTING.md followed
• AI usage, if any, follows AI_ASSISTANCE.md
• Tests added/updated (target: 65% overall coverage, goal 70%)
• Coverage ≥65% for changed packages
• Docs updated (if user-facing)
• CHANGELOG.md updated (if user-facing change)
• Conventional commit messages used
• OTel spans on significant functions
• Evidence generated for auditable operations
• No secrets hardcoded

Related Issues

Fixes #117

Testing

N/A - Markdown documentation updates only. Formats verified visually.

Release Note Draft (for user-facing changes)

• Problem solved: Added explicit security boundaries and limitations to the repository to build credibility and buyer trust.
• Who should care: Security teams, CTOs, and operators evaluating Talon's trust model.
• How to verify: Read the new LIMITATIONS.md guide linked in the README.
• Upgrade/migration impact: None.

AI Assistance Disclosure

• AI tooling used: Gemini (Drafting assistance)
• Human verification performed: Human-reviewed the tone to ensure "under-claimed" language and verified the structure perfectly aligned with the maintainer's requested outline in the issue comments.

[sergeyenin]

Hi @naffee , thank you submitting PR. Can you base it on the actual version of main? I would appreciate that.