chore(release): v0.7.28

[argszero]

Summary

Release v0.7.28 — a version bump only (Cargo.toml + Cargo.lock) plus the CHANGELOG
entry for the 20 PRs merged since v0.7.27 (#274–#293). No production code is touched by
this PR.

• No schema change (still 15) and no config change (config.toml needs no sync).
• No cache-bust bump here: every UI PR in this batch already advanced its own ?v= token,
  so ui/index.html ends this version at i18n.js / app.js ?v=20260924-2,
  api.js ?v=20260914-13, data.js / style.css ?v=20260914-11.
• cargo test 376 passed / 0 failed (was 308 at v0.7.27), cargo fmt --check rc=0,
  cargo clippy --all-targets -- -D warnings rc=0.

What is in v0.7.28

The batch continues the same rule the previous releases have been applying — one fact, one
source; the displayed quantity must equal the consumed one — and this time extends it to two
carriers it had not covered: state that outlives its boundary, and scope that does not match
the scope that is claimed.

area	PRs
Identity boundary: overlays outside #app, module-level transaction-view state	#278, #279
Transactions view: token spelling, trend grain, server-side sort, pager window	#281, #282, #284, #285
Payload receipt must be written by the request that issued it	#289
Language layer + overlay/form teardown (help panel, login label, toast level)	#288, #290, #293
Input & display parity (password unit, forgot-password message, marketplace count unit, ops balance column, type prose, CSV CR, disabled chips)	#275, #276, #277, #280, #283, #287, #291
New feature: transaction trend card switches between four metrics	#292
Test fidelity: the SSE split-boundary test now covers what it claims	#274

17 new state_gate invariants were added in this batch; each one derives its expected values from
the code under test rather than snapshotting them.

Related Issue

No linked issue — this is a release commit for the merged work above.

Changes

• Cargo.toml / Cargo.lock: 0.7.27 → 0.7.28
• CHANGELOG.md: new v0.7.28 section
• Config / data-structure changes are reflected in the example files (n/a — none)

Tests

• cargo test all pass (376 passed / 0 failed)
• cargo fmt --check passes
• cargo clippy --all-targets -- -D warnings passes
• Unit tests added/updated (n/a — release-only change)

Checklist

• Branch name follows the convention (release/)
• Commit message follows Conventional Commits (chore(release): v0.7.28)
• Single responsibility, minimal change