refactor(agent-presets,web): copy-only preset authoring with a path to the files

The web YAML editor is gone. agentPreset.write (arbitrary composition
text) became agentPreset.copy { from, agentPreset, name? }: a host-side
whole-directory copy of ids the host resolves itself — symlinks
dereferenced, modes re-tightened to owner-only with owner-execute kept,
metadata rewritten to keep the source's description but never its name or
roster order. No composition text or path crosses the wire in either
authoring direction, and the entryListSchema/!!js concern dissolves with
assertComposition itself.

The settings section becomes: a read-only viewer over shipped
compositions, a copy dialog (id + optional display name) as the only
create entry, delete for custom rows, and a location action leading into
the preset's own files — agentPreset.openDocument { agentPreset } resolves
the directory host-side and opens it natively, or answers
{ opened: false, path } for the row to show as text where the deployment
has no desktop. agentPreset.list reports hasDocument beside authorable;
the gateway's nativeOpen config pins the capability where
canOpenNativePath platform detection would mislead. The privileged set is
now read/copy/openDocument/remove.

With files as the only composition editor, standing mounts grew
stamp-keyed generations: ensureStanding compares the composition file's
mtime+size and starts the next generation for later sessions, while every
joined session keeps the generation it runs on.

New keyless web lane (agent-preset-authoring, overlay pins
nativeOpen: false so goldens render one branch on every platform) drives
view/copy/reveal/delete end to end; the real-composition CLI e2e switches
to copy semantics.

packages/client/connection/README.md

@@ -2,7 +2,7 @@
 
 English | [中文](README.zh.md)
 
-Wire consumer layer: the client plugin's apply mounts `ctx.connection` (shared api client + current-page loopback state + single-consumer stream-loop starter); the export face carries the wire contract types, the `AbstractApiClient` seam, and the loop's sink/config types. The browser carrier uses HTTP POST for unary and respond operations and opens one downlink-only WebSocket each for `events.mux` and `events.host`; the in-process carrier satisfies the same two-stream abstraction. The Host half owns the single `/api` route and its Fetch bridge; a registered TypeRT interceptor claims its Remote endpoints before the API Proxy fallback. Loopback hostname classification stays package-internal: the `/api` Host fence and WebSocket upgrades use it directly, while other client plugins consume the derived `ctx.connection.isLoopback` state. The node half's `/api` route pins the privileged method set (`host.pickDirectory`, `host.openPath`, and the whole configuration plane — `settings.describe`/`openDocument`/`update`/`replace`/`mutate` and `credentials.describe`/`set`/`unset`; reads and native actions included, since describing returns the exposed configuration, opening acts on the Host desktop, and probing an arbitrary reference reports where a credential comes from — and the agent-preset authoring plane, `agentPreset.read`/`write`/`remove`, since a composition names the plugins a session runs, so reading one is reconnaissance and writing one is arbitrary capability; `agentPreset.list` and `agentPreset.select` stay out — the roster carries only ids and trust, and choosing a preset grants nothing `session.create`'s own `agentPreset` did not, over a default that already carries bash) to loopback by passing the trust fence with an empty trust list — a declared `trustedHosts` authority reaches every other method, while these stay loopback-local until a real authentication layer exists. The platform carriers and ConnectionController loop are package-internal; apply selects and drives them. The downlink boundary is documented in the [WebSocket downlink carrier Agent Note](../../../.agents/notes/implemented/architecture/2026-08-04-websocket-downlink-carrier.md); the protocol contract is api-contracts v3 §3.
+Wire consumer layer: the client plugin's apply mounts `ctx.connection` (shared api client + current-page loopback state + single-consumer stream-loop starter); the export face carries the wire contract types, the `AbstractApiClient` seam, and the loop's sink/config types. The browser carrier uses HTTP POST for unary and respond operations and opens one downlink-only WebSocket each for `events.mux` and `events.host`; the in-process carrier satisfies the same two-stream abstraction. The Host half owns the single `/api` route and its Fetch bridge; a registered TypeRT interceptor claims its Remote endpoints before the API Proxy fallback. Loopback hostname classification stays package-internal: the `/api` Host fence and WebSocket upgrades use it directly, while other client plugins consume the derived `ctx.connection.isLoopback` state. The node half's `/api` route pins the privileged method set (`host.pickDirectory`, `host.openPath`, and the whole configuration plane — `settings.describe`/`openDocument`/`update`/`replace`/`mutate` and `credentials.describe`/`set`/`unset`; reads and native actions included, since describing returns the exposed configuration, opening acts on the Host desktop, and probing an arbitrary reference reports where a credential comes from — and the agent-preset authoring plane, `agentPreset.read`/`copy`/`openDocument`/`remove`, since a composition names the plugins a session runs, so reading one is reconnaissance, and copy/remove/openDocument manage the roster and drive the host desktop (authoring is copy-only, so none of them accepts composition text or a path); `agentPreset.list` and `agentPreset.select` stay out — the roster carries only ids and trust, and choosing a preset grants nothing `session.create`'s own `agentPreset` did not, over a default that already carries bash) to loopback by passing the trust fence with an empty trust list — a declared `trustedHosts` authority reaches every other method, while these stay loopback-local until a real authentication layer exists. The platform carriers and ConnectionController loop are package-internal; apply selects and drives them. The downlink boundary is documented in the [WebSocket downlink carrier Agent Note](../../../.agents/notes/implemented/architecture/2026-08-04-websocket-downlink-carrier.md); the protocol contract is api-contracts v3 §3.
 
 ## /api browser-trust fence