fix: preserve tags across plugin updates

[yattdev]

Changing the installed Tags package could make intact shared tags appear lost when a transient action failure switched the UI to an empty private compatibility store. Shared state now remains authoritative through network and 502/503/504 failures, retries only the idempotent catalog read, and still falls back on the host's definitive undeclared-action 404.

Important Changes

• Preserve the last confirmed shared catalog and task applications during runtime replacement, with bounded retries and generation checks that prevent obsolete requests from reviving timers after re-initialization or destruction.
• Lock the persisted plugin id, state capabilities, shared action contract, and agent-tags workspace key with automated tests.
• Document the supported in-place update and compatible rollback lifecycle, including destructive uninstall behavior and the pre-0.9 compatibility boundary.

Validation

• make test — Go tests and 132/132 JavaScript tests passed; fresh runtime 828 ms.
• make fmt
• make vet
• make package-host
• go test -count=1 -race ./server/...
• Fresh Chromium QA at 0f80d2175b4cfde5ede60c05f738fc0253200aa3 verified that human and agent chips remain visible during a structured HTTP 503 and after recovery.
• Current GitHub jobs fail before feature tests because the unpinned Kandev SDK now changes go.mod/go.sum during go mod tidy; package building reports that module updates are required.

Screenshots

During transient HTTP 503; the last confirmed shared catalog remains visible and no legacy write occurs:

After the shared read succeeds; the same catalog is restored without reload or user mutation:

Possible Improvements

Medium risk: pin or regularly refresh the Kandev SDK dependency set so upstream transitive dependency changes do not break otherwise unchanged plugin workflows.

Checklist

• I have performed a self-review of my code.
• I have manually tested my changes and they work as expected.
• My changes have tests that cover the new functionality and edge cases (make test).
• I updated README.md if this changes user-facing behavior.