cordis plugin runtime poc

this branch isolates the direct cordis implementation from the three-way plugin runtime experiment.

shape

• real cordis Context, Fiber, inject, provide, effect, and isolate behavior
• dependency-aware differential reconciliation preserves unchanged fibers
• staged isolation symbols allow old and candidate providers to overlap transactionally
• plugin-owned contributions are published as frozen snapshots
• cleanup attempts every dependent-first fiber and aggregates finalizer failures

cordis satisfies the contract, but the adapter still needs a t3-specific planner, transaction model, snapshot format, and structural type shim. cordis rc.8's extensionless declaration re-exports do not resolve under this repository's esm settings.

proved

• 31 tests cover dependency order, blocking, rollback, cycles, unchanged fiber reuse, order-insensitive declarations, activation implementation replacement, active callback reentrancy, synchronous callback microtasks, plain-function callback returns, prompt activation-context expiry, descendant async tasks, late activation-context calls, queued input snapshots, observer isolation, cleanup reporting, unusual ids and slots, and immutable snapshots
• manifest validation enforces semver, prevents entrypoint path escape, and keeps mobile declarative
• the demo exercises activation, replacement, teardown, and a 250-plugin chain

run

vp test run packages/plugin-runtime-poc/src
vp run --filter @t3tools/plugin-runtime-cordis-poc typecheck
vp run --filter @t3tools/plugin-runtime-cordis-poc demo

this is an isolated runtime poc. it does not load packages, add a sandbox, expose plugin rpc, or wire product ui.