📝 Rework CLI README to match mobile style with brand diagrams

[Miyamura80]

Summary

Reworks the cli README to match the mobile client's layout and adds real,
brand-styled diagrams and section icons. Documentation only; no code or behavior
changes.

Changes

• Restructure README.md to mirror mobile/README.md: SealGate banner, centered
  title, inline-icon intro, a command table for the sealg surface, a
  Configuration env-var table, and Requirements / Quick Start / Python client /
  Agent Skills / Credits / License sections.
• Add two SealGate-brand SVG diagrams in .github/assets/ (blueprint grid, cyan
  wireframe boxes, reused SealGate wordmark and agent marks):
  • architecture.svg: agent/shell → stateless sealg binary (crates/cli +
    crates/engine) → HTTPS/MCP → gateway that owns all policy, trifecta, and PII
    enforcement → connectors, with doctor shown as a local-only branch.
  • lifecycle.svg: what list / call / doctor each do on the wire, with exit codes.
• Add a cohesive line-icon set in .github/assets/icons/ (network, flow, package,
  bolt, gear, puzzle, code, scale) plus a terminal.svg header icon, wired into
  the section headings the way mobile puts an icon next to headings.
• Replace the leftover Tauri-Template banner with the on-brand SealGate Hackbox
  banner already used in the mobile repo.

Testing

• Documentation-only change; Rust tests and workspace are untouched.
• All new SVGs validated as well-formed XML and rendered to confirm layout.
• README local link/asset references verified to resolve; no em-dashes in any authored file.

Note: make ci's check_ai_writing reports em-dashes, but all of them are
pre-existing in unrelated source files (crates/**, CLAUDE.md) already on
main; this PR introduces none.

Related Issues

N/A (documentation refresh)

🤖 Generated with Claude Code

https://claude.ai/code/session_017c8tZFMUWA3pXVw9aFwMpx

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Generated by Claude Code

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Summary by cubic

Reworks the cli README to match the mobile client's layout and swaps the outdated Tauri-Template banner for the on-brand SealGate Hackbox banner. Documentation only; no code or behavior changes.

• Adds the architecture.svg and lifecycle.svg diagrams plus a line-icon set, all under .github/assets/.
• Restructures sections to mirror mobile: centered title, sealg command table, Configuration env-var table, and Requirements / Quick Start / Python client / Agent Skills / License sections.
• make ci's check_ai_writing flags em-dashes, but they're all pre-existing in unrelated files already on main; this PR introduces none.

^{Written for commit e4be964. Summary will update on new commits.}

[qodo-code-review]

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[cubic-dev-ai]

No issues found across 13 files

_{Re-trigger cubic}

[Miyamura80]

Heads-up on the one red check, Cargo Deny (job):

error[vulnerability]: RUSTSEC-2026-0285 — rustls 0.23.36
Solution: Upgrade to >=0.23.45  (cargo update -p rustls)
advisories FAILED, bans ok, licenses ok, sources ok

This is not caused by this PR. The diff is documentation and assets only (README.md + .github/assets/**); it does not touch Cargo.toml, Cargo.lock, or deny.toml. The flagged rustls 0.23.36 pin is identical on main, so this advisory is red on the base branch too, independent of this change. All functional checks (Formatting, Clippy + Tests, build, knip) are green.

I'm deliberately not widening this docs PR with a dependency bump. The fix belongs in its own change:

cargo update -p rustls   # 0.23.36 -> >=0.23.45, lockfile only

Happy to open that as a separate security PR if you'd like.

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Generated by Claude Code