feat: resolve latest patch for a major.minor version (#293)

* feat: resolve latest patch for a major.minor version

Allow the version input and version-file entries to be a major.minor value like
3.14 / v3.14, resolving to the newest available patch (e.g. v3.14.4).

Resolution probes the download host directly: sequential HEAD requests for
helm-v{major}.{minor}.{n} against downloadBaseURL, taking the highest that
returns 200. Works with any file-serving mirror and needs no token or extra
dependency, and cannot resolve to a version that is not downloadable. Only
major.minor.n URLs are probed, so prereleases are never considered.

- Add isMajorMinorShaped, helmPatchExists, and resolveLatestPatchVersion.
- Walk stops after 3 consecutive 404s (look-ahead) to tolerate a skipped patch
  number, with a 100-probe safety cap; hitting the cap throws instead of
  returning a bogus version.
- Wire resolution into run() and relax getVersionFromToolVersionsFile to accept
  a major.minor value.

* feat: support .x/.* wildcards and harden patch probing

Extend the major.minor latest-patch resolution to accept wildcard patch syntax (`3.12.x`, `v3.12.x`, `3.12.*`), matching the syntax requested in Azure/setup-helm#109.

The following smaller fixes were made based on Copilot review feedback:

- helmPatchExists now treats only 404 as "patch absent"; any other non-2xx status (403/405/429/5xx) and network errors are thrown, so rate-limiting, outages, or a host that disallows HEAD can no longer be misread as a missing patch (which could yield a stale version or a false "No Helm releases found").
- Clarify the version-file validation error to reflect that both a full version and a major.minor value are accepted, with concrete examples.
- Tests: use vi.spyOn(globalThis, 'fetch') instead of vi.stubGlobal so restoreAllMocks() reliably restores fetch and the mock never leaks across tests; add coverage for wildcards and the non-404 throw path.

* ### feat: single-request listing fast-path + semver.org validation

**Listing fast-path (with fallback).** Following the discussion about enumeration, `resolveLatestPatchVersion` now first tries a single Azure Blob container-listing request against the download host (which `get.helm.sh` backs), and only falls back to the sequential HEAD-probe walk if the host doesn't return a valid listing. Enumeration and download stay on the **same host**, so there's no risk of resolving a version the host can't serve, and it still works on any mirror.

- Default host: resolution now takes **1 request** instead of ~8 probes (verified live: `3.9`→`v3.9.4`, `3.12`→`v3.12.3`, `3.14`→`v3.14.4`, `3.16`→`v3.16.4`, `2.17`→`v2.17.0`).
- Non-listing hosts fall back to probing; prereleases and `.sha256` sidecars are excluded from the listing parse.

**semver.org regex.** Per review feedback, `isSemVerShaped` now uses the official regex from semver.org (with an added optional leading `v` for Helm tags) instead of the hand-rolled one.

Added tests for the listing fast-path, the fallback, and a non-listing response; full suite is green (`npm test`, `typecheck`, `format-check`).

.gitignore

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