Release prep: v0.1.2

[lsaether]

Summary

Cuts v0.1.2, consolidating everything merged since v0.1.1:

• replay generation boundary after successful session/load (PR fix: segment replay after session/load #19, fixes Segment replay history across canonical ACP session changes #17)
• replay recordedAt / replaySeq provenance under _meta.amux (PR fix: persist replay metadata timestamps #20, closes Persist mux-recorded replay timestamps in history metadata #18)
• opt-in subscriber → agent _meta.amux trace propagation via --meta-propagate (PR feat: add opt-in _meta.amux propagation #21, closes Use _meta passthrough for amux trace fields #6)
• live session/list response decoration with mux metadata (PR Decorate session/list responses with live amux metadata #23, closes Decorate session/list responses with live mux metadata #22)
• HTTP control-plane session discovery at GET /acp/sessions?cwd=... (PR Add control-plane session discovery #24, closes Control-plane session discovery (list sessions without WS-attaching first) #10)

What's in this release-prep PR

File	Change
Cargo.toml	Bump package version from 0.1.1 to 0.1.2.
Cargo.lock	Refresh the root package version to 0.1.2.
README.md	Status bump from v0.1.1 to v0.1.2.
CHANGELOG.md	Move Unreleased notes into a dated v0.1.2 — 2026-05-23 entry with Added / Fixed / Notes.

Release notes summary

• Cold-start session discovery: GET /acp/sessions?cwd=<optional> without WS attach.
• Replay log no longer mixes pre-load and loaded-session history for late joiners.
• Replay frames carry mux-owned recordedAt + replaySeq provenance.
• --meta-propagate provides opt-in request trace metadata under params._meta.amux.
• Live session/list entries are decorated with additive _meta.amux mux state.

After this merges

1. Tag v0.1.2 on main and push the tag.
2. Create the GitHub release using the drafted release notes.
3. Leave the remaining backlog as-is: Self-handle fs/* and terminal/* in the mux instead of broadcasting them to subscribers #2 (high-priority fs/terminal self-handling), Watch upstream: open ACP RFD PRs of interest #7 (upstream RFD watch), and shelved/conflicting PR Align with RFD #533 (multi-client session attach) #3.

Test plan

• cargo fmt -- --check
• cargo check
• cargo clippy --all-targets -- -D warnings
• cargo test
• cargo test -- --list — expected current count: 84 tests (34 unit + 50 integration)