bug(pi): mem_search fails with 'could not reach' for queries with underscores/hyphens returning 0 results

[killo3967]

Bug Description

mem_search from Pi (gentle-engram v0.1.10 + engram v1.20.0) reports "gentle-engram could not reach the Engram HTTP server" for specific queries — but Engram is actually running and healthy. The failure is deterministic by query pattern, not intermittent.

Environment

• gentle-engram: 0.1.10
• engram: 1.20.0
• OS: Windows 11
• Agent: Pi (el Gentleman)
• Shell: Git Bash

Steps to Reproduce

// These work:
mem_search(query: "a", project: "epub-repair")        // ✅
mem_search(query: "nailgun", project: "epub-repair")   // ✅

// These FAIL with "could not reach":
mem_search(query: "lowercase_tags", project: "epub-repair")          // ❌
mem_search(query: "empty_lang extender", project: "epub-repair")     // ❌
mem_search(query: "rsc032_fallback BMP", project: "epub-repair")     // ❌
mem_search(query: "PKG-008 fixer ADR-0005", project: "epub-repair")  // ❌

Expected Behavior

Return "No memories found" (empty result) like the CLI does.

Actual Behavior

gentle-engram could not reach the Engram HTTP server at http://127.0.0.1:7437.
The Pi-native mem_* tools are registered, but the native memory provider is not
currently responding. Run mem_doctor or restart Engram.

Diagnostic Evidence

Engram CLI — works perfectly

$ engram search "lowercase_tags" --project epub-repair
→ No memories found for: "lowercase_tags"    (instant)

$ engram search "PKG-008 fixer ADR-0005" --project epub-repair
→ No memories found for: "PKG-008 fixer ADR-0005"    (instant)

HTTP API — works perfectly

$ curl "http://127.0.0.1:7437/search?q=lowercase_tags&project=epub-repair&limit=5"
→ HTTP 200 | 26ms | body: "null"

Health check — always OK

$ curl http://127.0.0.1:7437/health → 200
$ mem_doctor → 4/4 checks OK
$ mem_context → works always
$ mem_save → works always

Root Cause Hypothesis

The bug is in the gentle-engram Pi plugin layer (bridge between Pi mem_search tool and Engram HTTP API), not in Engram core. The plugin appears to mishandle HTTP responses for queries that:

1. Return zero results (empty/null response)
2. AND contain special characters (_, -)

The plugin interprets a valid empty response as a connection failure and reports "could not reach" instead of returning empty results.

Pattern Analysis

Query	Has special chars?	Returns results?	mem_search
"a"	No	Yes	✅
"nailgun"	No	Yes	✅
"lowercase_tags"	Yes (_)	No	❌
"PKG-008 fixer..."	Yes (-)	No	❌

This was discovered while investigating intermittent Engram failures during an epub-repair session. The user initially suspected parallelism (multiple mem_search calls in one <invoke> block), but systematic testing proved the bug is query-dependent, not concurrency-dependent.