fix(chat): drop backend commands that collide with a desktop alias

[AmirF194]

Fixes #817

Problem

The slash-catalog reconciliation filtered backend agent commands against desktop command names but not desktop aliases — an asymmetry with its two sibling filters (desktop-target aliases and the alias map both already exclude desktop aliases).

A backend command whose name equals a desktop alias therefore survived into the merged catalog and was registered as an agent command; when the desktop command later registered that same name as its alias, createSlashCatalog threw Duplicate slash command alias and the app crashed on startup.

Today the only trigger is a backend /commands command, since desktop help aliases commands — but it's the same startup-crash class as the /compact collisions in #802 / #804 / #813.

Fix

• Extract the reconciliation out of Chat.tsx's useMemo into a pure, exported reconcileSlashCatalog so the merge is unit-testable (mirrors the tested-helper approach from fix(chat): drop canon alias that duplicates a pairs command #808).
• In that helper, exclude any backend command whose name matches a desktop name OR alias.

Desktop authoring still wins deterministically (/commands resolves to the desktop help command), and createSlashCatalog's throw-on-collision guard for genuine desktop-vs-desktop authoring conflicts is left intact.

Tests

Added reconcileSlashCatalog specs in commandCatalog.test.ts:

• backend /commands colliding with help's commands alias no longer throws, and resolves to the desktop command
• desktop wins over a same-named backend command
• non-colliding backend commands are still exposed

vitest run src/renderer/src/screens/Chat/slash/ → 23 passed. tsc --noEmit clean. lat check passes.

[greptile-apps]

Greptile Summary

This PR fixes a startup crash where a backend /commands command collided with the help desktop command's commands alias, by extracting the slash catalog reconciliation into a pure reconcileSlashCatalog helper and extending the backend-command filter to cover desktop aliases in addition to desktop names.

• commandCatalog.ts: Adds reconcileSlashCatalog, a self-contained, exported function that performs the full backend-vs-desktop merge; the key fix is !desktopAliases.has(command.name) alongside the existing !desktopNames.has(command.name) guard.
• Chat.tsx: Slims the slashCatalog useMemo from ~40 lines to a single reconcileSlashCatalog(...) call; logic is identical but now lives in a testable unit.
• commandCatalog.test.ts: Adds three reconcileSlashCatalog specs — alias-collision regression, desktop-wins-over-same-named-backend, and non-colliding backend command passthrough — all matching the fix.

Confidence Score: 5/5

Safe to merge — the change is a targeted extraction and single-predicate fix with a direct regression test that would have caught the original crash.

The refactoring is mechanical — the reconciliation logic from Chat.tsx is moved verbatim into reconcileSlashCatalog, with exactly one predicate added (!desktopAliases.has(command.name)) to close the reported gap. Three new unit tests cover the regression, the desktop-wins case, and the non-colliding passthrough. No new control paths were introduced; createSlashCatalog's throw-on-collision guard for genuine authoring conflicts remains intact.

No files require special attention.

Important Files Changed

Filename	Overview
src/renderer/src/screens/Chat/slash/commandCatalog.ts	Adds reconcileSlashCatalog with the corrected alias-collision guard; logic is a clean extraction of the existing Chat.tsx useMemo with the single-line alias check added.
src/renderer/src/screens/Chat/Chat.tsx	useMemo reduced to a thin call-site; dependency array unchanged; behavior is preserved exactly.
src/renderer/src/screens/Chat/slash/commandCatalog.test.ts	Three new specs for reconcileSlashCatalog cover the regression, desktop-wins, and passthrough cases; all build on existing test infrastructure.
lat.md/chat-commands.md	Documentation updated to describe reconcileSlashCatalog and clarify the two-layer reconciliation; accurate and consistent with the implementation.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[agentCommandCatalog] --> B[reconcileSlashCatalog]
    C[desktopCommands] --> B
    D[fallbackAgentCommands] --> B

    B --> E[agentCommandsFromCatalog]
    E --> F{discovered?}

    F -- yes --> G[discovered.commands]
    F -- no --> H[fallbackAgentCommands]

    G --> I[Filter: not in desktopNames AND not in desktopAliases NEW]
    H --> I

    E --> J[discovered.aliases]
    J --> K[desktopTargetAliases backend alias to desktop target]
    J --> L[pass-through aliases non-desktop source and target]

    K --> M[agentCommands array]
    I --> M

    M --> N[createSlashCatalog]
    C --> N
    L --> N

    N --> O[SlashCommandCatalog]

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flowchart TD
    A[agentCommandCatalog] --> B[reconcileSlashCatalog]
    C[desktopCommands] --> B
    D[fallbackAgentCommands] --> B

    B --> E[agentCommandsFromCatalog]
    E --> F{discovered?}

    F -- yes --> G[discovered.commands]
    F -- no --> H[fallbackAgentCommands]

    G --> I[Filter: not in desktopNames AND not in desktopAliases NEW]
    H --> I

    E --> J[discovered.aliases]
    J --> K[desktopTargetAliases backend alias to desktop target]
    J --> L[pass-through aliases non-desktop source and target]

    K --> M[agentCommands array]
    I --> M

    M --> N[createSlashCatalog]
    C --> N
    L --> N

    N --> O[SlashCommandCatalog]

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_{Reviews (2): Last reviewed commit: "Merge branch 'main' into pr/818" | Re-trigger Greptile}

[greptile-apps]

The desktopAliases Set is populated from raw alias strings (e.g. "commands"), while backend command names arriving from agentCommandsFromCatalog are already normalized by normalizeName (lowercased, leading slashes stripped). If a desktop command ever defines an alias with a leading slash (e.g. "/commands") or mixed casing, desktopAliases.has(command.name) will return false for the normalized backend name and the collision guard will silently miss it — leaving createSlashCatalog to throw at runtime. The same inconsistency affects desktopNames, which is also un-normalized. Normalizing both sets at construction time closes the gap without changing any behavior for the current, well-formed inputs.

Suggested change

	const desktopNames = new Set(desktopCommands.map((command) => command.name));
	const desktopAliases = new Set(
	desktopCommands.flatMap((command) => command.aliases ?? []),
	);
	const desktopNames = new Set(desktopCommands.map((command) => normalizeName(command.name)));
	const desktopAliases = new Set(
	desktopCommands.flatMap((command) => (command.aliases ?? []).map(normalizeName)),
	);

[fathah]

Reviewed and verified locally — approving.

Confirmed the bug is live on main: replicated the current Chat.tsx merge logic with a backend catalog exposing /commands against the desktop help command (which aliases commands) — it throws Duplicate slash command alias: /commands exactly as described in #813. So this is not covered by #808, which fixed the backend-internal pairs-vs-canon collision; this PR closes the remaining backend-command-vs-desktop-alias axis.

Verification performed:

• The reconcileSlashCatalog extraction is a faithful move of the Chat.tsx useMemo logic — the desktopTargetAliases and alias-map filters are byte-identical; the only behavioral change is the added !desktopAliases.has(command.name) guard, which is the fix.
• Mutation-tested the regression test: removing just the alias check makes it fail with the exact production error; with the fix, all 23 slash tests pass.
• Mixed-case squatting is covered — normalizeName lowercases backend names before the filter.
• The catalog: null fallback path now also gets alias protection — a strict improvement over main.
• createSlashCatalog's throw-on-collision stays intact for genuine desktop-vs-desktop authoring conflicts, consistent with the layering established in #808.
• tsc clean (the one i18n/index.ts error is pre-existing on main), eslint clean on touched files (the 3 exhaustive-deps warnings in Chat.tsx are pre-existing, outside this diff), lat check passes, and the lat.md update accurately documents the new reconciliation layer.

Nice work keeping the fix at the reconciliation boundary and making the merge unit-testable.