feat(std-net): add TLS certificate inspection

[larimonious]

Summary

• Adds std/net.tls_info(host, opts?) for bounded TLS certificate inspection.
• Returns certificate subject/issuer details, common names, SANs, validity timestamps, days remaining, serial, signature algorithm, TLS protocol/cipher, chain length, and validation status.
• Keeps private/special target policy aligned with the rest of std/net.
• Adds local TLS fixture coverage, typechecker coverage, generated stdlib docs, AI guide docs, and an opt-in public example.

Verification

• cargo test --locked
• cargo build --profile dev-release --locked
• ./target/dev-release/ntnt docs --generate
• ./target/dev-release/ntnt validate examples/
• ./target/dev-release/ntnt lint examples/
• ./target/dev-release/ntnt validate examples/std_net_tls.tnt
• ./target/dev-release/ntnt lint examples/std_net_tls.tnt
• NTNT_NET_TLS_EXAMPLES=1 ./target/dev-release/ntnt run examples/std_net_tls.tnt
• git diff --check
• independent cold review

[greptile-apps]

Greptile Summary

This PR adds TLS certificate inspection to std/net. The main changes are:

• New tls_info(host, opts?) native function with certificate metadata and validation status.
• Rustls-based TLS connection, certificate parsing, and root-store validation.
• Private target policy support aligned with existing network helpers.
• Typechecker coverage, stdlib documentation, and an opt-in public TLS example.
• Local TLS fixture tests for metadata collection when validation fails.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.
• The latest TLS timeout fix now uses a shared deadline through the TCP connect and nonblocking handshake loop.
• Certificate validation uses the observed certificate chain rather than a second connection.

Important Files Changed

Filename	Overview
src/stdlib/net.rs	Adds tls_info and updates TLS handshake handling to use nonblocking I/O with a shared deadline.

_{Reviews (4): Last reviewed commit: "fix(std-net): enforce TLS handshake dead..." | Re-trigger Greptile}