feat(slash): /rename, plus tier-contrast and cursor follow-ups

[hakula139]

Summary

Bundles the /resume picker follow-ups with a /rename slash command and a chat-input chrome simplification.

/rename lets you set a session title manually — bare opens a single-line modal pre-filled with the current title; /rename <title> applies directly. After a manual rename, the background AI title generator no-ops for the rest of the session so a slow Haiku response can't overwrite the user's pick. Renames before the first prompt defer the on-disk write: the JSONL file isn't created until a real message lands, so a session that's only renamed (then quit) leaves nothing behind, and one that does have a header-only file on disk can still be resumed.

Two follow-ups land alongside it:

• Tier contrast. The /resume picker's secondary text (project / id / time) was nearly indistinguishable from dim. Brighten the muted slot across all five built-in themes so the muted / dim / text triplet reads as three distinct steps.
• Simpler input chrome. Drop the empty-buffer placeholder copy entirely (matching Claude Code's bare prompt). The arg-mode [id] ghost text stays but now sits one column after the cursor, mirroring ratatui_textarea's built-in placeholder layout. Net 74 fewer lines in input.rs plus the has_queued / sync_input_queue_hint plumbing the placeholder used to drive.

The slash-command popup descriptions for the five dual-mode commands also converge on a single short verb-first phrase, since the parameter placeholder is already shown by the row's usage() next to the name.

Design decisions

• Defer the write, don't filter at flush time. A /rename before the first prompt produces a header + Title entry but no message. Rather than writing those out and stripping them on next resume, WriterStatus::Pending { header, deferred_title } holds them in memory and only opens the JSONL on the first non-empty flush. Empty sessions die with the actor; non-empty sessions get a single atomic flush.
• Single source of truth for manual-title state. manual_title_set lives on SharedState only. The actor reads / writes it through a &SharedState borrow (passed into absorb); the title generator's pre-check goes through the same flag. This closes the race where Haiku finishes between /rename arriving and the actor draining its channel, and avoids the "two correlated bools" smell of a parallel field on SessionState.
• try_defer_title returns Option<String>, not Result<(), String>. The rejected title is routed back to the caller for normal-path queueing, not surfaced as an error. Option says that directly: Some(t) hands the title back, None parks it in the deferred slot. Avoids both the inverted-Result-reading smell and the clippy::large_enum_variant hit from holding a 272-byte Entry in WriterStatus. Last-wins is preserved (a second Some overwrites the first).
• Resume bail on pre_sanitize_len > 0 && messages.is_empty(). Header + Title-only sessions sanitize down to zero messages but should still resume — the title is meaningful state. Folding data.title.is_some() into the first_user_prompt_seen check keeps the title alive across the next message.
• SlashContext::with_title borrow over LiveSessionInfo field. The status-bar title isn't part of the persisted config snapshot — adding it to LiveSessionInfo would mean syncing two sources of truth across SessionRolled / Title events. A read-only Option<&str> parameter keeps the data flow obvious for the one command that needs it.
• Mutating in both forms. /rename <title> could in principle dispatch mid-turn, but routing it as Mutating matches /clear, /init, /resume — a single deferral rule keeps the dispatcher simple and the user model consistent.
• Slash-command popup wording. description() and usage() are rendered side by side, so spelling the parameter inside the description duplicates information the row already shows. The five dual-mode commands also split between two prose templates ("Open the X picker or switch directly with /cmd <param>" vs. "Verb the noun — /cmd for X, /cmd <param> to Y"). Land on the same shape claude-code and codex use: a single short verb-first phrase, no parameter mention, no UI-mechanism framing.
• Brighten muted, don't darken text. Bumping Catppuccin from Overlay0 to Subtext0 (and Material's equivalent) lifts the secondary tier without disturbing existing snapshots' text rendering.
• Drop placeholder, lean on the textarea's primitive. The previous fix overlaid a Paragraph to work around ratatui_textarea reserving col 0 for its cursor cell. Removing the placeholder altogether eliminates the hand-roll, and shifting the arg-mode hint by one column lets the OS-native cursor lead the dim text — the same layout the textarea's built-in set_placeholder_text produces.

Changes

File	Description
agent/event.rs	Add UserAction::Rename { title }.
agent.rs	Route Rename through the mid-turn warn-log catch-all.
main.rs	apply_rename helper: persist via set_manual_title, surface I/O failure, emit SessionTitleUpdated.
session/state.rs	WriterStatus::Pending { header, deferred_title } | Active(SessionWriter) | Broken state machine; try_defer_title returns Option<String> (Some(t) routes the title to the normal queue, None parks it); flush_entries reconstructs Entry::Title { source: UserProvided, updated_at: now() } at flush time when deferred_title is set. New // ── try_defer_title ── unit section covers Pending overwrite, Active reject, Broken reject. Resume contract on SessionState::resumed reworded as a precondition.
session/handle.rs	SharedState.manual_title_set: AtomicBool is the single source of truth; SessionHandle::set_manual_title latches before dispatch and exposes a manual_title_set accessor. Resume bail loosened to pre_sanitize_len > 0 && data.messages.is_empty() ("(likely corrupt)" parenthetical dropped — sanitize-prunes-everything is also legitimate); data.title.is_some() folds into first_user_prompt_seen. Tests cover the latch contract on healthy and dead-actor dispatch, plus title-only resume with title preservation across the next message.
session/handle/testing.rs	acks_then_drops covers the SetManualTitle or-pattern arm.
session/actor.rs	absorb now takes &SharedState. The SetManualTitle arm marks the shared flag, then either parks the title via try_defer_title (returns None) or queues a Title { source: UserProvided } entry (returns Some); AppendAiTitle short-circuits when shared.manual_title_set(); Record passes the same flag into queue_message_entries. New tests cover last-wins on two SetManualTitles and positional ordering of header / title / message.
session/title_generator.rs	Pre-check manual_title_set after parse_title to skip the actor round-trip when the user has already renamed.
slash.rs	Register the new module.
slash/context.rs	SlashContext.title: Option<&str> plus with_title constructor; new() delegates with None.
slash/registry.rs	Add &RenameCmd to BUILT_INS (alphabetical).
slash/rename.rs	New: RenameCmd (Mutating, [<title>] usage) + RenameModal (single-line input, 80-char cap, Enter / Backspace / Esc handling), plus TestBackend render tests for layout, ellipsis truncation, cursor placement, and short-area cursor bail.
slash/{effort,model,theme,rename,resume}.rs	Tighten popup descriptions to a single verb-first phrase; the parameter placeholder is already shown by usage().
tui/app.rs	Route UserAction::Rename through apply_action_locally; pass the live status-bar title into SlashContext; drop sync_input_queue_hint.
tui/components/status.rs	Promote title() from #[cfg(test)] to production-visible.
tui/components/input.rs	Drop empty-buffer placeholder + has_queued plumbing; arg-mode [id] ghost text now paints one column past the cursor.
tui/theme.rs, tui/theme/loader.rs, themes/*.toml	Brighten the muted slot across the five built-in themes (Catppuccin Subtext0 and Material equivalents).
CLAUDE.md, README.md, docs/guide/slash-commands.md, docs/roadmap.md, docs/design/tui/cancellation.md	Surface /rename and trim the slash-commands guide; drop placeholder claims that no longer apply.
Snapshots	Catch up popup, app-frame, and input render baselines.

Test plan

• cargo build compiles cleanly
• cargo clippy --all-targets -- -D warnings — zero warnings
• cargo test — 1811 tests pass
• cargo llvm-cov --ignore-filename-regex 'main\.rs' — 98% line / 98% region coverage
• pnpm lint — Markdown
• pnpm spellcheck
• Manually exercised /rename, /rename foo, modal Enter on empty, Esc cancel, the AI-title race (rename mid-Haiku — manual wins, no flicker), and the empty-session round-trip (rename + quit leaves no file on disk; rename + message + quit + resume keeps the title)

[codecov]

Codecov Report

❌ Patch coverage is 98.74477% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/oxide-code/src/slash/rename.rs	97.42%	7 Missing ⚠️
crates/oxide-code/src/session/state.rs	97.95%	2 Missing ⚠️

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