* feat: Show cooldown report for pinned version installs
When a user installs a package with an explicit version (e.g.
npm install foo@1.2.3) and that version falls within the dependency
cooldown window, the cooldown block is now recorded and shown in the
report. Previously, the report only appeared when ALL versions of a
package were in cooldown (remaining == 0), causing pinned version
installs to fail with a confusing "version not found" error from the
package manager instead of a clear cooldown explanation.
Introduces InterceptorContext to carry per-execution data (pinned
versions) from the CLI command through the interceptor layer, keeping
it separate from long-lived dependencies like the analyzer and cache.
* fix: Normalize PyPI pinned version keys for cooldown lookup
CLI-provided package names (e.g. Flask_Cors) don't match the
URL-parsed form (flask-cors). Normalize keys once at construction
time so cooldown lookups match correctly.
* fix: Handle dots in PyPI package name normalization per PEP 503
denormalizePyPIPackageName already documented [-_.] replacement but
only handled underscores. Now also replaces dots with hyphens so
names like zope.interface match the URL-parsed form zope-interface.
* refactor: Extract shared cooldown stats recording into helper
Deduplicate identical stats-recording blocks from npm_cooldown.go
and pypi_cooldown.go into recordCooldownStats in cooldown.go.
* fix: Distinguish explicit version pins from auto-resolved versions
PyPI parsers resolve all packages to concrete versions (even without
a user-specified constraint), so HasVersion() was always true. Add
IsExplicitVersion to PackageInstallTarget, set it only when the user
provided an explicit constraint. Use it in proxy_flow.go to avoid
false pinned-version cooldown reports.
