dsh-sessionflow v1.2.0 — DSH 0.2.1-rc.5 / 0.2.2-alpha.2 channel compatibility

Channel compatibility follow-up (charter R1). Upstream dist-tags moved; this release admits both new channels so dsh plugin add works without ERESOLVE workarounds.

Verified channels

DSH	cordis	install resolves	DSH loads it	tool call answered
0.2.1-rc.5 (next)	~4.0.5	✅	✅	✅
0.2.2-alpha.2 (alpha)	~4.0.6-alpha.1	✅	✅	✅
0.2.0-rc.2	4.0.4	✅	✅	✅
0.2.1-alpha.4	4.0.5-alpha.2	✅	✅	✅
0.1.5-rc.3	4.0.2	✅	✅	✅

• peerDependencies name the new prerelease lines explicitly (node-semver's
  prerelease tuple rule made the old range exclude both).
• Windows: cold-start install → bundle → prepare → profile-layer gates plus a
  real bridge call against a live core (voyager 1.3.0, schema 1).
• Linux CI: full cold-start including the boot-load gate on both new channels.
• Bridge schema unchanged (1); tool surface unchanged (six sessionflow_*).

Full write-up: docs/release-v1.2.0.md. Install:
dsh plugin --profile <profile> add github:HarryHeYu/dsh-sessionflow