fix: model action-conditional requireds in ctx_callgraph/expand/graph/knowledge (#1008)

[andig]

Problem

Fixes #1008 (follow-up to #1005). These action-driven ctx_* tools declared little or nothing in required, so malformed calls passed schema validation and only failed at runtime — e.g. ctx_callgraph({}) and ctx_expand({}) both validate but can't do anything.

Fix

Model the mode/action-conditional requirements with JSONSchema allOf + if/then (draft 2020-12):

• ctx_callgraph: require action; callers/callees/risk need symbol; trace needs from+to.
• ctx_expand: search_all needs query; the default retrieve path needs id (selected via if.not, so ctx_expand({}) is now invalid while the documented ctx_expand(id=…) stays legal without an explicit action).
• ctx_graph: related/symbol/impact/neighbors/explain/path need path; action=path also needs to.
• ctx_knowledge: remember needs category + (value|content); pattern needs value; search needs query; gotcha needs trigger+resolution. Adds the content alias to the schema.

The requireds were derived from each tool's actual runtime checks, not just the issue's summary (e.g. remember really needs category too; bare recall stays valid).

These schemas are declarative — the server does not enforce them. They let MCP hosts and the model infer valid call shapes and reject bad calls early.

normalize_for_strict_validators now recurses into if/then/else so the new conditional sub-schemas keep the strict-validator guarantees (the required: [] / items: {} injection for OpenAI/SGLang-style backends).

QA step

Per @andig's request on the issue to make this a QA step for future schema changes, adds schema_qa_tests.rs: a regression test that locks each tool's conditional requireds in place, so a future schema edit that drops one fails CI instead of only surfacing at runtime.

Scope

ctx_search / ctx_execute conditional modeling (named in #1005's tally) remains open follow-up.

Tests

4 new schema-QA tests; 229 related tool/schema/normalizer tests pass. Existing behavior unchanged.

🤖 Generated with Claude Code

[yvgude]

Superseded by and integrated into #1013. The conditional schemas and real jsonschema QA were retained and extended to ctx_search and ctx_execute; the original commit/authorship remains preserved in the integrated history. Thank you.