feat(sessions): import and continue Codex and Zcode sessions

[kev1n77]

Summary

Bring Codex and Zcode histories into OpenBitFun's regular session navigation as read-only source views. Opening a source refreshes its history; the first send creates an independent native branch from the revision the user viewed.

• Read Codex rollouts, saved titles and resumed-thread identities, and Zcode's SQLite main-task histories without modifying the source applications.
• Discover enabled sources when a workspace opens, persist lightweight references, and preserve local names, archive state, removal/restoration and independent continuations. Imported tools render through read-only native cards.
• Preserve existing native imports, old index payloads, versioned caches and interrupted-history repair. Remove the unused manual import commands, grouped discovery APIs, associated DTOs/tests and obsolete locale strings; share the duplicated persistence fixture and regenerate capability projections.
• Keep search invalidation optional for SDK Host builds and allocate legacy materialization and turn startup futures on the heap so native admission and background results fit the default thread stack.

Type and Areas

Type: Feature, bug fix, UI/UX, docs, and tests.

Areas: Rust adapters, product contracts, core assembly/session persistence, desktop/Tauri, Web UI, capability registry, and localization.

Verification

Rebased onto upstream/main at c60d6a4d4. The two Installer conflicts retain the upstream ZIP implementation and frozen legacy-payload fixture; this PR no longer changes Installer files. Post-rebase validation on Windows:

• Installer cargo check, 7 native payload/extraction tests (including file and embedded legacy payloads), and 18 installer/Data Tools script tests passed.
• Capability generation check and diff whitespace checks passed. git range-diff confirms the four feature commits retain their session changes, with only the already-landed Installer patch removed.

Focused session validation completed before this rebase; the session implementation is unchanged by the rebase:

• Core external-session discovery/history suite: 41 passed, 2 optional installed-history checks ignored. Covers persisted compatibility, versioned history, native forks, ownership, source loss and removal/restoration.
• Codex reader: 14 passed, 2 optional installed-source checks ignored. Zcode reader: 12 passed, 1 optional installed-source check ignored.
• Session contracts and Product Operation Registry: 22 passed, including legacy candidate round trips and generated-registry equivalence.
• Frontend ecosystem, removed-session API and external-history notice: 175 passed across 14 files. pnpm run type-check:web passed.
• Capability generator check and 16 capability tests passed; i18n audit passed with zero warnings. Changed Rust formatting and diff whitespace checks passed.
• pnpm run check:core-boundaries passed in a clean verification checkout with the complete current PR applied.

Earlier CI regression checks for the retained SDK/stack fixes: SDK Host suites passed 87 tests; both previously overflowing dialog-admission and background-result tests passed with the default stack. The broader Core selection passed 187 tests with 4 ignored and the two existing Windows fixture failures described below.

Validation Limits

• check:web stops at 25 typography violations. The unchanged audit engine reproduced the identical 25 findings against a clean upstream-base checkout; type checking and focused UI tests passed separately.
• The earlier broader Core run found two existing Windows fixture issues: a remote-root test supplies a Windows path, and a goal-template test expects LF in a CRLF checkout. Both reproduced in the pre-fix executable and match upstream fixtures.
• Desktop integration tests were not rerun: the earlier executable failed before tests with STATUS_ENTRYPOINT_NOT_FOUND. Native GUI, SSH workspaces, Remote Connect/mobile/IM, Peer Device Mode and Detached Dispatch have not been exercised end to end. Unsupported source actions remain explicitly gated.

Reviewer Notes

Provider parsing stays in adapters; stable facts and operation policy stay in contracts; discovery and persistence remain with their existing owners. The retired manual prototype is not a consumer of the automatic discovery path. Existing imported data and native session protocols remain readable; source histories stay read-only.

Full source snapshots are retained to preserve viewed revisions. Large-history scan, paging and retention optimization remain outside this change.

Checklist

• Relevant verification and limitations are recorded above.
• User-facing strings, docs and generated capability projections match the active workflow.
• No temporary reports, logs, source transcripts or build outputs are included.