fix(session): route attach socket through symlink

[kurtisc]

Linked Issue

Closes #1465

Summary

Routes attach sockets through a symlink to avoid paths which are too long (i.e. >SUN_LEN)

Test Plan

export XDG_STATE_HOME="$HOME/$(printf '-%.0s' {1..80})"
mkdir -p "XDG_STATE_HOME"
nono run --detached -- yes

Checklist

• An issue exists and is linked above
• All commits are signed-off, using DCO
• All new code follows the project's coding standards (CLAUDE.md) and is covered by tests
• Public-facing changes are paired with documentation updates
• Release note has been added to CHANGELOG.md if needed

[github-actions]

PR Review Summary

Size

Metric	Value
Lines added	+308
Lines removed	-8
Total changed	316
Classification	Large (> 300 lines)

Affected crates

• crates/nono-cli — CLI changes. Verify argument parsing, flag documentation, and UX behaviour across supported platforms.

Blast radius — Contained

This PR touches: source code

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_{Updated automatically on each push to this PR.}

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.

[connrg]

lgtm

[nogent-nolabs-ai]

nogent code review

No blocking issues; 0 findings.

Findings: none flagged in scope.

_{Automated code + security review. CI already covers clippy, rustfmt, tests, cargo-audit and commit-lint.}