feat(cli): polish installation and upgrade progress UI

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Summary

Beautify installation and crabcode upgrade output using the supplied terminal reference: compact current/target version labels, whitespace, and an amber block/dotted progress row. Based directly on upstream main (bf5c111), independent of plugin PR #25.

• Shell/npm downloads show measured progress when size is known; unknown duration upgrades show Working rather than a fabricated percentage.
• Respect terminal width, NO_COLOR, TERM=dumb, and redirected output. Diagnostics stay on stderr; no alternate screen or cursor hiding.
• Keep in-app background upgrades captured and silent.
• Replace the stale Bash/cargo-first root install.sh with a POSIX prebuilt installer using real release archive names, SHA256 verification, staged atomic binary replacement, and installation receipts.
• Preserve flat/custom install destinations and historical cargo-dist cargo-home layouts. Reject mismatched receipts and invalid versions, and never silently substitute the latest release for a requested version.
• Drain npm download streams correctly, report truncation/write errors, and close progress on failure.
• Add just test-upgrade-ui; extend just test-release with shell installer coverage.

UI preview (plain-text structure)

Installed version: 0.0.14

Installing crabcode version: 0.0.15
████████..........................................  17%

This is a layout illustration, not a claim that v0.0.15 was installed. Package-manager upgrades use an indeterminate Working row because those tools do not expose a reliable end-to-end completion percentage. Existing cargo-dist-generated release installer assets are not rewritten.

Validation

• cargo fmt --all -- --check, git diff --check, cargo check: pass.
• cargo test --bin crabcode upgrade:: -- --test-threads=1: 25 pass.
• bun test --timeout 30000 scripts/release-workflow.test.ts scripts/install-ui.test.ts npm/install.test.js: 80 pass. An initial final rerun hit Bun's default 5-second test deadline under concurrent builds; the bounded 30-second rerun passed.
• cargo build --bin crabcode + bun test scripts/upgrade-ui.test.ts: 13 pass; exercises the compiled CLI in real PTYs and isolated install fixtures.
• node --test npm/install.test.js: 13 pass.
• Prettier check for changed JS/TS and sh -n install.sh: pass.
• Real GitHub v0.0.14 release installed in a disposable directory, checksum verified, and --version confirmed. Host installation untouched.

Full serial Rust unit suite: 1,844 passed, 1 failed, 3 ignored. The failure is ui::components::chat::tests::test_edit_tool_renders_codex_style_diff_summary, which hardcodes /Users/carlo/Desktop/Projects/crabcode/README.md and expects a relative filename on this checkout. The chat source is unchanged in this PR; the same failure was reproduced on unmodified upstream bf5c111 in a separate worktree. Not claiming a globally green suite.

Design audit and limits

Audited after implementation as requested. No further design changes requiring approval: inherited terminal theme, one amber accent, no panels/badges/decorative emoji, actual loading/error/no-op states, and bounded progress widths. Terminal palettes are user-controlled, so universal color contrast cannot be guaranteed; NO_COLOR is supported.

Runtime tested on macOS. Linux/Windows execution and OS-signal cancellation during a download were not specifically exercised. No dependencies added. Do not merge automatically.