Vastly simplify auth contexts

[toothbrush]

https://entire.io/gh/entireio/cli/trails/471

TLDR: Cache entiredb-cluster→entire-core mappings

Problem

Resolving which login context to use for an entire:// cluster mixed two concerns: which control plane fronts a cluster (stable infra) and which of your accounts to use (per-user). When several contexts were eligible and none was active, it picked one by last-save order and persisted that guess as a binding — so the choice was somewhat arbitrary, and the stored state ended up asymmetric and confusing.

99% happy path: unchanged

• One account → exactly one eligible context → used automatically. No prompt, no extra step.
• No added latency — /.well-known is cached; first op per cluster fetches once, as before.
• No migration / re-login — existing contexts.json loads as-is; the obsolete cluster_contexts key is ignored and removed.
• A new error fires only on genuine ambiguity (2+ accounts on the same core, none active) — previously a silent guess (e.g., admin@core, paul@core both match), now a clear "pick one."

Change

• Cache only the objective cluster → [core_urls] fact (in cluster_cores.json, 24h TTL, stale-fallback). The matching account is recomputed locally every op, never persisted.
• Selection: active context if eligible → else the sole eligible one → else (2+ eligible, none active) a one-line error listing them and pointing at entire auth use, instead of guessing.
• Drops the now-defunct bind/unbind surface.

---

Note

High Risk
Changes how every entire:// operation picks credentials (auth path); wrong selection or stale core cache could block git or use the wrong account until the user runs entire auth use or clears cache.

Overview
This PR splits cluster auth into infra vs identity: only which cores front a cluster is cached (cluster_cores.json, 24h TTL, stale fallback on discovery failure); which login context to use is recomputed every git op and never written to disk.

entire:// resolution loads cores from cache or /.well-known, then picks a context: active context if its core is eligible → else the only eligible context → else an error listing candidates and pointing at entire auth use (no silent multi-account guess).

Removed persisted cluster_contexts, BindCluster / File.Resolve, and entire auth unbind plus cluster-binding output from entire auth contexts. Logout / delete no longer auto-advance current_context to another stored identity.

Shared discovery cache I/O is refactored for the new cores file; git-remote-entire passes the discovery cache dir into resolution. .gitignore adds /git-remote-entire.

^{Reviewed by Cursor Bugbot for commit edb6bdb. Configure here.}

[Copilot]

Pull request overview

This PR refactors entire:// auth resolution to cleanly separate infrastructure discovery (which cores front a cluster) from identity selection (which local login context to use), removing the previously persisted cluster→context bindings and eliminating silent “best guess” selection when multiple accounts match.

Changes:

• Introduces a new cluster_cores.json cache (24h TTL + stale fallback) for cluster→core URL mappings, and refactors cache file I/O to be reusable across cache files.
• Updates cluster auth resolution to recompute eligible contexts on each operation: prefer active context if eligible → else use the sole eligible context → else error on ambiguity (no persisted binding).
• Removes the cluster binding surface (cluster_contexts, bind/unbind functionality, and related CLI output/tests), and changes logout/delete behavior to never auto-switch identities.

Reviewed changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/entireclient/discovery/cluster_cores.go	Adds the new cluster→core URL cache type and helpers (load/modify/get/set).
internal/entireclient/discovery/cluster_cores_test.go	Tests for cache round-trip, freshness/staleness behavior, and copy semantics.
internal/entireclient/discovery/cache.go	Refactors cache locking + JSON read/write into shared primitives used by multiple cache files.
internal/entireclient/contexts/contexts.go	Removes cluster_contexts state + APIs and changes deletion semantics to clear current_context rather than auto-advance.
internal/entireclient/contexts/contexts_test.go	Updates tests to reflect removal of bindings and new delete/current semantics.
internal/entireclient/clusterdiscovery/resolve.go	Switches resolution to use cluster cores cache + deterministic context selection, erroring on ambiguity.
internal/entireclient/clusterdiscovery/resolve_test.go	Adds coverage for cores caching, stale fallback, ambiguity errors, and updated selection rules.
cmd/git-remote-entire/main.go	Passes cache dir into resolution and updates description of the new resolution flow.
cmd/entire/cli/auth/contexts_test.go	Updates logout/remove-all behavior tests to reflect removal of bindings.
cmd/entire/cli/auth/context_store.go	Removes binding cleanup paths; ensures logout clears current context without switching identities.
cmd/entire/cli/auth.go	Removes entire auth unbind command registration.
cmd/entire/cli/auth_context.go	Removes cluster bindings listing and unbind command implementation from entire auth contexts.
cmd/entire/cli/auth_context_test.go	Removes tests that asserted binding visibility and unbind behavior.
.gitignore	Ignores the git-remote-entire binary at repo root.