fix(pi-fff): preserve path/exclude in fuzzy grep fallback (#697)

[gustav-fff]

Closes #697

Root cause

packages/pi-fff/src/index.ts:727 invoked the fuzzy fallback with the raw pattern, discarding the constrained query built at src/index.ts:665-667 via buildQuery (src/query.ts:80). Since query is the only carrier of the normalized path include and !<exclude> clauses, the fallback searched the entire index — leaking matches from excluded directories or files outside the requested path.

Fix

Pass the constrained query to the fallback picker.grep call instead of pattern. The fallback still broadens matching (fuzzy vs. plain) but no longer broadens scope.

Steps to reproduce

Setup on origin/main (pre-fix):

git checkout 05a35c6d4856455393a2dc8aadaeae4b2823ddf6
cd packages/pi-fff

Fixture:

/tmp/fff-repro/
  target.json          # does not contain "needle"
  sessions/history.jsonl  # contains "needle"

Call ffgrep via pi-fff with:

{
  "pattern": "needle",
  "path": "/tmp/fff-repro/target.json",
  "exclude": "sessions/",
  "context": 0,
  "limit": 5
}

Actual (pre-fix):

[0 exact matches. Maybe you meant this?]
sessions/history.jsonl
  1: ...needle...

Expected:

No matches found

The sessions/ directory is explicitly excluded AND is outside the requested path (a specific file). The fuzzy fallback discarded both constraints because it re-ran with pattern (needle) rather than the constrained query (target.json !sessions/ needle).

How verified

• Unit tests: bun test in packages/pi-fff/ — 44 pass, 0 fail.
• Diff inspection: fallback now consumes the same query string as the primary search; the only difference between the two picker.grep calls is mode: "fuzzy" vs. the auto-detected mode.
• Behavior under maintainer's original intent (broadening pattern matches across the workspace when no path/exclude is set) is preserved because buildQuery returns just pattern when no constraints are supplied.

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[dmtrKovalenko]

@gustav-fff update the pr to preserve it ONLY if there is no extension (I mean when there is path like /some/file/path.ts INSIDE the cwd or any aux pickers we use the whole picker fuzzy match) but if there is a directory we use the standard aux picker finding and preserver the queries

[gustav-fff]

[triage-bot] DIRECTED: pushed d500af2.

Behavior split by the last segment of params.path:

• File path (matches \.[a-zA-Z][a-zA-Z0-9]{0,9}$) — fuzzy fallback re-runs with the raw pattern, broadening across the whole picker (workspace or aux). Rationale: caller pinned a specific file that returned zero exact hits — likely misnamed — so widening scope is what the user wants.
• Directory / glob / absent path — fuzzy fallback keeps the constrained query so it cannot leak from excluded dirs or out-of-scope trees.

Extension detection uses the same regex as normalizePathConstraint in packages/pi-fff/src/query.ts:49, so file vs. directory classification stays consistent across query build + fallback.

Tests: bun test in packages/pi-fff/ — 44 pass, 0 fail.

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