feat(plugin-detail): show Markdown plugin details on bundle and market entry pages

Plugins bundle pages and Discover entry pages show the plugin's long
description first, as Markdown with images, in a height-limited region
without its own heading. The document is the file locale meta.detail
names, otherwise the package README, otherwise (market entries only)
the declared repository's README.

The new dsh-plugin-detail library selects documents and reads local
package directories and npm file CDNs without state. plugin-manager
reads installed and offered bundles through readBundleDetail; plugin-market
reads market entries through readEntryDetail, single-file APIs, and a
size-limited partial clone cache serialized across processes. Raw HTML is
omitted, relative links stay text, and relative images load from Host
routes with a sandbox CSP.

docs/module-graph.md

@@ -19,6 +19,7 @@ flowchart TD
     pkg_native_command["native-command"]
     pkg_output_retention["output-retention"]
     pkg_package_manifest["package-manifest"]
+    pkg_plugin_detail["plugin-detail"]
     pkg_plugin_market_index["plugin-market-index"]
     pkg_timeout["timeout"]
     pkg_util_code_language["util-code-language"]
@@ -1303,6 +1304,7 @@ flowchart TD
   pkg_api_session_controller --> pkg_workspace
   pkg_plugin_market --> pkg_plugin_manager
   pkg_plugin_market --> pkg_settings
+  pkg_plugin_market --> pkg_subprocess
   pkg_plugin_market --> pkg_tools
   pkg_plugin_market --> pkg_typert_protocol
   pkg_headless --> pkg_agent
@@ -1448,6 +1450,7 @@ flowchart TD
 | [`native-command`](../packages/util/native-command) | `util` | — |
 | [`output-retention`](../packages/util/output-retention) | `util` | — |
 | [`package-manifest`](../packages/util/package-manifest) | `util` | — |
+| [`plugin-detail`](../packages/util/plugin-detail) | `util` | — |
 | [`plugin-market-index`](../packages/util/plugin-market-index) | `util` | — |
 | [`timeout`](../packages/util/timeout) | `util` | — |
 | [`util-code-language`](../packages/util/code-language) | `util` | — |
@@ -1763,7 +1766,7 @@ flowchart TD
 | [`tool-subagent`](../packages/subagent/tool-subagent) | `subagent` | [`agent`](../packages/core/agent), [`agent-preset-registry`](../packages/preset/agent-preset-registry), [`llm`](../packages/llm/llm), [`scope`](../packages/core/scope), [`session`](../packages/core/session), [`session-projection`](../packages/session/session-projection), [`subagent`](../packages/subagent/subagent), [`system-prompt`](../packages/core/system-prompt), [`tools`](../packages/core/tools) |
 | [`tool-subagent-control`](../packages/subagent/tool-subagent-control) | `subagent` | [`agent`](../packages/core/agent), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent), [`tools`](../packages/core/tools) |
 | [`api-session-controller`](../packages/api/session-controller) | `api` | [`agent`](../packages/core/agent), [`agent-default-model`](../packages/core/agent-default-model), [`agent-preset-registry`](../packages/preset/agent-preset-registry), [`api-gateway`](../packages/api/gateway), [`attachment`](../packages/attachment/attachment), [`client-connection`](../packages/client/connection), [`client-file-upload`](../packages/client/file-upload), [`commands`](../packages/interaction/commands), [`credentials`](../packages/credentials/credentials), [`file-reference`](../packages/context/file-reference), [`fs`](../packages/fs/fs), [`llm`](../packages/llm/llm), [`native-command`](../packages/util/native-command), [`scope`](../packages/core/scope), [`session`](../packages/core/session), [`session-persistence`](../packages/session/session-persistence), [`session-projection`](../packages/session/session-projection), [`session-projection-cache`](../packages/session/session-projection-cache), [`session-query`](../packages/session-query/session-query), [`session-title`](../packages/session/session-title), [`settings`](../packages/settings/settings), [`skill`](../packages/skill/skill), [`subagent`](../packages/subagent/subagent), [`typert-protocol`](../packages/typert/protocol), [`typert-registry`](../packages/typert/registry), [`util-time`](../packages/util/time), [`util-values`](../packages/util/values), [`util-workspace-path`](../packages/util/workspace-path), [`working-directory`](../packages/session/working-directory), [`workspace`](../packages/workspace/workspace) |
-| [`plugin-market`](../packages/boot/plugin-market) | `boot` | [`plugin-manager`](../packages/boot/plugin-manager), [`settings`](../packages/settings/settings), [`tools`](../packages/core/tools), [`typert-protocol`](../packages/typert/protocol) |
+| [`plugin-market`](../packages/boot/plugin-market) | `boot` | [`plugin-manager`](../packages/boot/plugin-manager), [`settings`](../packages/settings/settings), [`subprocess`](../packages/subprocess/subprocess), [`tools`](../packages/core/tools), [`typert-protocol`](../packages/typert/protocol) |
 | [`headless`](../packages/bundle/headless) | `bundle` | [`agent`](../packages/core/agent), [`agent-default-model`](../packages/core/agent-default-model), [`fs`](../packages/fs/fs), [`llm`](../packages/llm/llm), [`permission-presets`](../packages/interaction/permission-presets), [`sandbox-policy`](../packages/sandbox/sandbox-policy), [`session`](../packages/core/session), [`session-query`](../packages/session-query/session-query), [`subagent`](../packages/subagent/subagent), [`user-approval`](../packages/interaction/user-approval) |
 | [`compaction-basic`](../packages/compaction/compaction-basic) | `compaction` | [`agent`](../packages/core/agent), [`commands`](../packages/interaction/commands), [`compaction`](../packages/compaction/compaction), [`compaction-tool-result-pruner`](../packages/compaction/compaction-tool-result-pruner), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`token-meter`](../packages/llm/token-meter) |
 | [`session-reference`](../packages/context/session-reference) | `context` | [`agent`](../packages/core/agent), [`compaction`](../packages/compaction/compaction), [`llm`](../packages/llm/llm), [`output-retention`](../packages/util/output-retention), [`session`](../packages/core/session), [`session-projection`](../packages/session/session-projection), [`session-projection-cache`](../packages/session/session-projection-cache), [`session-query`](../packages/session-query/session-query), [`session-title`](../packages/session/session-title), [`spill`](../packages/spill/spill), [`subagent`](../packages/subagent/subagent), [`system-prompt`](../packages/core/system-prompt), [`typert-protocol`](../packages/typert/protocol) |