build(deps): update Everruns and carry reasoning artifacts

[chaliy]

What changed

Moves the pinned Everruns workspace from 66c20400 to 74841cbb (everruns
0.18.2 to 0.21.0, everruns-host 0.20.1 to 0.21.0, everruns-provider 0.22.0).

ContentPart gained two variants, File and Reasoning, so Svit's message
boundary now carries file references and provider reasoning artifacts without
host translation. Everruns is a sibling project, so its types are re-exported
directly rather than wrapped: svit re-exports ReasoningContentPart and
ReasoningText.

Effect on callers: a host reading Svit::messages or recent_messages may now
observe ContentPart::Reasoning and ContentPart::File on assistant messages.
No effect on guest scripts — reasoning never reaches the guest.

Lampa renders readable reasoning on its own thinking channel and file parts by
filename.

A second commit updates rustls 0.23.43 to 0.23.45 and rustls-webpki 0.103.13
to 0.103.15 for RUSTSEC-2026-0285, which published on 2026-09-14 and failed this
PR's dependency audit. The advisory affects main equally, so this is a ported
fix rather than fallout from the Everruns bump; it is a lockfile-only change on
transitive dependencies reached through reqwest.

Why

Keeping the pinned sibling dependency current. The bump is not mechanical: the
two new ContentPart variants broke Lampa's exhaustive match, and reasoning
artifacts carry opaque provider replay state that needed a decision about where
it may and may not travel.

A reasoning part carries readable text alongside signature, encrypted, and
item_id. Every current provider verifies that state against the exact position
it was issued in, so the canonical event stream stores the part whole and the
projection returns it unchanged rather than flattening or dropping it.

Before / after

Five new tests, all failing-to-passing in the sense that the surface they pin
did not exist before the bump:

• reasoning_artifacts_survive_the_canonical_event_projection
  (crates/svit/src/reasoning.rs) appends an assistant message carrying a
  reasoning part through the event log and asserts the part returns identical,
  and that neither the signature nor the encrypted payload appears in /thread.
• readable_reasoning_renders_on_its_own_channel and
  summary_reasoning_joins_its_segments (crates/lampa/src/tui.rs) cover both
  readable forms, Plain and Summary.
• opaque_reasoning_never_reaches_the_screen asserts opaque-only reasoning is
  neither drawn nor allowed to pull a tool-only message out of the compact tool
  row.
• file_attachments_render_with_their_filename covers file parts with and
  without a filename, and asserts the file id is never drawn.

Security

• Threat IDs reviewed or added: TM-AUD-001 reviewed, none added.
• Isolation, rollback, limit, and diagnostic effects: reasoning replay state
  stays host-owned. No builtin exposes thread messages and /thread remains
  bounded metadata, so the bump adds no guest-visible surface and needs no new
  threat ID. A reasoning part is ordinary guest-shaped JSON measured against the
  same process limits as any other event payload, so validate_event_payload
  fails closed on an oversized one exactly as before. Diagnostics narrow rather
  than widen: Lampa renders only ReasoningContentPart::display_text, and
  signature and encrypted are replay state rather than content and are never
  drawn.
• New ambient authority: none.

Risk

• Low
• What can break: the reasoning part is new on assistant messages, so a host
  that assumed every ContentPart on an assistant message was text or a tool
  call will now see a variant it does not handle. Within this repository the
  only such consumer is Lampa, which this change updates.
• Dependency review: cargo-audit was installed in this environment and
  cargo audit now exits clean, reporting only the four warnings deny.toml
  already allows. cargo-deny was not installed locally, so the new transitive
  crates (chrono-tz, fs2, phf, phf_shared) and the jsonschema 0.49 to
  0.54 upgrade were checked by hand against deny.toml and need no new
  allow-list entry; CI's Check licenses and sources step is the authoritative
  check and passes on the current head. That step was skipped on the first
  commit because the advisory failure short-circuited the job ahead of it.

Checklist

• Tests added or updated
• just pre-pr passes — all gates green, including audit once
  cargo-audit was installed; cargo-deny runs in CI only
• Executable examples updated when public behavior changes — all 11
  acceptance examples pass unchanged; no example behavior changed
• Knowledge and limitations updated when durable decisions change —
  knowledge/log.md, knowledge/foundations/process-model.md, CHANGELOG.md
• Threat model updated for new attack surfaces — reviewed; no new attack
  surface, so no new threat ID

https://claude.ai/code/session_01WxSsxEaLaW6Pa29HVzjfoe