[Bug] Sessions from older releases can't be resumed or opened after upgrading (unknown preset standard-tools; v0 subagent descriptor v2 refused)

[MovieMaker93]

Hi, and thanks for dsh. After upgrading a long-lived install from 0.1.5-rc.1 to 0.1.7-rc.2, many older Sessions can no longer be continued, and some subagent transcripts can't be opened at all. I traced both to their cause and checked that master (639ed01, 0.2.0-rc.2) still behaves the same. I know external pull requests aren't accepted; fixes with tests are on a fork in case they're useful.

Environment: Linux, npm install of @deepseek-ai/dsh, dsh web as a systemd service, 197 stored Sessions written by several releases since August.

1. A Session whose recorded preset no longer exists can't be resumed

100 of 129 top-level Sessions were created with a directory preset from ~/.dsh/.agent-presets/standard-tools. 0.1.7 no longer reads that directory, so continuing any of them fails:

agent-preset/not-found: Unknown agent preset: standard-tools
details: { agentPreset: "standard-tools", available: ["standard", "ptc", "minimal", "cordis"] }

session/create with the existing sessionId and cwd reaches createOrAdopt → composeAgent(storedPreset) → agentPresets.resolve("standard-tools"), which throws. Switching the Session to another preset isn't possible either, because select refuses once the Session has started (agent-preset/locked). Reading the transcript still works. The 0.1.7-rc.2 upgrade guide doesn't mention that directory presets stopped loading.

Reproduce: create a Session under preset X and send one message; remove the X definition; restart; call session/create with that sessionId and its cwd.

Proposed change (one commit on a fork, diff against master): an explicit aliases map on agent-preset-registry, so a deployment can say which declared preset a retired ID resolves to:

- id: agent-preset-registry
  config:
    default: standard
    aliases:
      standard-tools: standard

• resolve, mount/retain and read follow the alias; the roster lists only declared presets.
• A declaration whose ID is also an alias fails to register; an alias whose target isn't declared reports both IDs.
• The "Unknown agent preset" message says how to map a removed preset.
• Tests: 3 new cases in registry.spec.ts (fail on master, pass with the change); 100% coverage of src/index.ts. README (en/zh) and its translation record updated.

Until then, the workaround is to declare a preset-standard-tools row whose plugin list copies preset-standard. With that row, the same Session resumes (verified on a throwaway 0.1.7-rc.2 instance).

2. Format v0 subagent transcripts with descriptor v2 are refused

19 subagent child Sessions fail to open on 0.1.5, 0.1.7-rc.2 and current master; 0.2.0-rc.2 ships the same checks:

SessionFormatUnsupportedError: subagent/descriptor 5 uses unsupported descriptor version 2; source v0 artifact remains unchanged

Releases 0.0.1-rc.1 (2026-08-10) through 0.1.1-rc.2 (2026-08-21) wrote subagent/descriptor v2 into format v0; v3 arrived on 2026-08-24 (#2663) and only added the optional agentReasoningEffort. Two checks refuse v2:

• assertReleasedEventPayload in session-format-v0-to-v1 throws for any non-3 descriptor in payload generation 0;
• subagentDescriptorValue in payload-validation.ts, which the v2→v3 edge also uses, accepts only version: 3.

The V3→V4 catalog facts already accept descriptor v1–v3, and docs/session-format-status.md states that alpha, beta and RC releases establish released Session-format obligations.

Proposed change (one commit on a fork, diff against master): accept descriptor v2 in the shared payload validation, reject agentReasoningEffort on v2, and keep refusing descriptor versions no release wrote into format v0. Committed generations stay unchanged.

• Tests: 5 new cases in session-format-v0-to-v1/tests/validation.spec.ts and one end-to-end test in session-persistence-jsonl/tests/catalog-migration.spec.ts (a V0 child with descriptor v2 opens through read and write access, none and zstd). All fail on master and pass with the change; 100% coverage of the two changed files; the session-format, catalog and JSONL suites pass (1934 tests).
• On a copy of the 197 real Sessions, master fails to open 19; with the change all 197 open for read and for write.

Both changed packages type-check, as do the host packages that depend on the preset registry; I didn't run the full-repository build, which needs more memory than my server has. Happy to adjust either change or split it differently if that helps.