cli(upgrade): fix 404 — drop version from tarball filename (#352)

[danielraffel]

Summary

pulp upgrade 404'd on every run because the CLI built download URLs
using pulp-<version>-<platform>-<arch>.<ext> and x86_64, while the
release workflow uploads assets as pulp-<platform>-<arch>.<ext> with
x64. This PR pins the URL shape to the release workflow and adds a
Catch2 regression guard so the two can't drift silently again.

This is the second half of #352; the first half (pulp pr → shipyard pr
shim) is in-flight as #376. Fixing both gets pulp upgrade and pulp pr
back to parity with their documented behavior.

Changes

• tools/cli/upgrade_url.hpp — new header-only URL/asset builder so
  the regression test can pin the naming convention without linking
  cmd_misc's transitive CLI deps.
• tools/cli/cmd_misc.cpp — replace the local helper (which baked
  the version into the filename and used x86_64) with a call into
  pulp::cli::pulp_upgrade_url_for().
• test/test_cli_upgrade_url.cpp — 6 Catch2 cases against real
  v0.14.0 release naming, including one that explicitly fails if a
  future refactor re-introduces the version in the filename.

Convention (pinned by the header + tests)

Asset = "pulp-<platform>-<arch>.<ext>"   (no version in the filename)
URL   = ".../releases/download/v<version>/<asset>"
arch  = "arm64" | "x64"                   (NOT "x86_64")
ext   = "zip" for windows, "tar.gz" otherwise

Mirrors .github/workflows/release-cli.yml.

Test plan

• New pulp-test-cli-upgrade-url runs green locally (10 assertions,
  6 cases).
• cmake --build build --target pulp-cli succeeds (refactor
  compiles end-to-end).
• CI green on macOS / Ubuntu / Windows via shipyard.
• Manual spot check post-merge: pulp upgrade against a real
  release downloads successfully.

Closes #352.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Handle Windows zip upgrade payloads end-to-end

After this change, Windows now targets pulp-windows-*.zip assets, but the rest of cmd_upgrade still follows the Unix tarball path (tar -xzf) and later expects ${tmp_dir}/pulp. The release workflow packages Windows as pulp.exe inside a zip, so on Windows the download can succeed and then fail during extraction or binary lookup, leaving pulp upgrade broken for that platform.

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