docs(langsmith): add filter-traces page for the rebuilt tracing filter UI - #5793

Why

The LangSmith tracing filter UI has been rebuilt (Milestone 1 of the filter revamp, targeting rollout Sept 10). The chip-and-dropdown filter builder is replaced by a single search bar with a query language, the trace/tree filters are replaced by a scope selector, and the Filter Shortcuts pane has moved from the bottom of the right sidebar to a collapsible panel on the left. filter-traces-in-application describes none of this, so it needs a full rewrite rather than edits.

Linear: DOC-1570

What this PR does

Adds src/langsmith/filter-traces.mdx. It documents:

• The search bar query language: field:value clauses, negation with -, full-text ~, wildcards, existence, numeric comparisons, and ranges
• AND/OR/NOT precedence, implicit AND on whitespace, and value quoting
• The field reference, split into run fields and the disjoint set of thread fields available in the Thread scope
• Dot notation for input/output/metadata JSON keys and feedback subfields
• What full-text search indexes, and how it differs from key-path filtering
• The four scopes (Thread, Root run, Single run, Any run), the available scopes and default per table selection, combining scopes across filter rows, and the "Not applied" badge
• The collapsible Shortcuts and Stats panels
• Saved views, including automatic translation of views saved with the previous syntax

Also adds src/snippets/langsmith/filtering-experience-note.mdx, imported by both this page and the ClickHouse page, which routes readers between the two experiences.

Includes five light/dark screenshot pairs: the search bar, the scope selector with its sample-trace preview, two filter rows on different scopes, the Shortcuts panel, and match highlighting inside an open trace.

SDK and API changes are out of scope for the initial release, so the page points at trace-query-syntax for the structured query language.

A five-persona documentation review was applied on top of the first draft. It moved scopes ahead of the syntax reference, moved the indexing limits to the end, added Examples and Troubleshoot a query sections, and removed three unsourced claims. make lint_prose and make broken-links both pass.

How the details were verified

The field tables, scope labels, per-view defaults, and operator support come from the smithdb-filter-lang WASM schema and the FiltersRevamp components in langchain-ai/langchainplus, re-verified against current origin/main after the reviewer's feedback. Product behavior that is not visible in the code (indexing limits, legacy-view translation, rollout cohorts) comes from the reviewer's answers on DOC-1570.

Two items where the code contradicted a review comment, both raised on the review threads:

Deliberately omitted

• The ClickHouse-era indexing limits (250-character cap, 100 unique keys per run, 2-character minimum token). SmithDB does not use them. Replaced with the SmithDB figures. The ClickHouse page keeps the old numbers, which remain correct for that backend.
• Filtered Only, Switch to raw query, and the copy-filter button. Confirmed removed from the product, not relocated.
• What Most relevant and Show All do when no filter is applied. Undocumented anywhere, including on the old page. The page states only that both are disabled while a filter is applied, which was verified in production.

Needs careful review

1. Scope terminology. The page uses "table selection" for the Threads/Traces/Runs control and "scope" for the selector left of the search bar, to keep the two ideas distinct. Worth a check that this matches how the team talks about it.
2. The metadata row. Metadata accepts ~ per the schema but is indexed separately from the full-text token index, so the row leads with metadata.<key> and describes ~ as searching metadata values. Confirm that phrasing is right.

Follow-ups (not in this PR)

• Swap the src/docs.json nav entry to langsmith/filter-traces; the page is currently an orphan
• Add a /langsmith/filter-traces-in-application redirect, which requires moving the ClickHouse page off that slug
• Remap 5 anchored inbound links: #filter-operators becomes #operators in billing.mdx:163, #create-and-apply-filters becomes #build-a-query in engine.mdx:148 and threads.mdx:292, and two links to #example-filtering-for-tool-calls have no successor
• Rewrite prose on pages that describe the previous filter UI. Three found so far, and only two are anchored links, so a link-only sweep will miss them:
  • threads.mdx:292 names the Add filter button and Save view
  • engine.mdx:148 refers to the "filter editor"
  • rules.mdx:85 says "Automation rule filters work the same way as filters applied to traces in the project", which becomes false for SmithDB users once this page is live, because rule filters keep the previous chip-based builder
• Audit dashboards.mdx for the same problem. dashboards.mdx:101 describes chart filters as "one + Filter in the Filter & group panel", the previous builder, which will read as inconsistent beside this page
• Decide what replaces #example-filtering-for-tool-calls, which online-evaluations-code.mdx and online-evaluations-llm-as-judge.mdx both link to
• Fix the ClickHouse page's trace-view-filter-light/dark.png alt text, which describes the three view modes while the images show the old Filters field list
• Replace the ClickHouse page's filter-bar-search-* and filter-shortcut-pane-* images, which show the previous UI
• Add a self-hosted version line to the availability snippet once v0.17 is settled
• Reinstate a "what next" section once charts, evaluators, and rules adopt the new filter UI. The PRD scopes this revamp to the tracing page and table only, so today there is no way to carry a filter into those panes and the syntax does not transfer

AI disclosure

Drafted by Claude Opus 5 via Claude Code. Source material: the DOC-1570 Linear issue and its attachments (demo walkthrough frames, transcript, UI screenshots), the filter revamp PRD and filter syntax spec, and the langchain-ai/langchainplus implementation. Product behavior in the page was checked against the implementation or against the reviewer's written answers; see "How the details were verified".