feat(cli): thread Config into the share path

[ecalifornica]

Part of #184 (PR 8 of the plan there). Stacked on the export PR (branch robert/config-export). path-cli only.

What

• run() passes &Config to cmd_share. share_explicit, derive_session, and resolve_destination take it as a parameter. The two Config::load() sites in cmd_share are gone.
• The picker bundle and the freshness-stat bundle come from providers::harness_bundle(config).
• HarnessBundle::from_environment is deleted. share was its last caller.
• sync::fresh_cache_id takes &Config. No record surface in the sync engine loads a Config per call.
• share_config::resolve_remote takes &Config and locates config.toml through Config::config_dir. The ~/ expansion of a rule's dir still uses the free home_dir().
• cache.rs and cmd_pathbase.rs still resolve their directory through the free config_dir(). Later PRs own them.
• Upload-side environment reads are untouched: $PATHBASE_URL, the credentials file, and the cmd_export Pathbase machinery keep their current form.

Emscripten

• All touched code and the deleted from_environment are native-only (cfg(not(target_os = "emscripten"))), so the emscripten build is unaffected.

Behavior change

• None. The Windows pi note in feat(cli): thread Config through the import path #198 applies to share as well. This PR does not change that resolution further.

Tests

• The resolve_destination unit tests take a Config carrying the temp config dir. cmd_share sets no environment variable and needs no TEST_ENV_LOCK guard.
• The engine test fresh_cache_id_tracks_source_and_eviction passes the jail Config.
• tests/integration.rs share_configured_repo_requires_login and share_configured_repo_uploads_when_authed run the binary with $TOOLPATH_CONFIG_DIR set, so Config reaches resolve_remote end to end.

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