feat(php): Add Core Valkey Search commands

[edlng]

feat(php): add Valkey Search commands (ftCreate, ftDropIndex, ftList, ftSearch, ftInfo, ftAggregate, ftAliasAdd, ftAliasDel, ftAliasUpdate, ftAliasList)

Summary

Adds FT.* commands for Valkey Search across both standalone (ValkeyGlide) and cluster (ValkeyGlideCluster) clients.

This is the first of two PRs splitting the original valkey-search branch. The CI changes (Docker-based server startup for the Search module) follow in a separate PR.

Issue link

Closes #163

Features / Behaviour Changes

• ftCreate — create a search index with schema definition and options (ON, PREFIX, SCORE, LANGUAGE, vector fields, etc.)
• ftDropIndex — drop an existing index
• ftList — list all indexes
• ftSearch — run a search query with options (RETURN, PARAMS, SORTBY, LIMIT, NOCONTENT, shard/consistency flags)
• ftInfo — get index metadata with optional scope (LOCAL, PRIMARY, CLUSTER) and shard flags
• ftAggregate — run an aggregation pipeline (GROUPBY, REDUCE, SORTBY, APPLY, FILTER, LIMIT, LOAD, PARAMS, DIALECT)
• ftAliasAdd — add an alias to an index
• ftAliasDel — remove an alias
• ftAliasUpdate — point an alias at a different index
• ftAliasList — list all alias-to-index mappings

Implementation

Follows the existing command pattern in the repo:

• PHP stubs in valkey_glide.stub.php and valkey_glide_cluster.stub.php
• Shared argument builders and FFI dispatch in valkey_glide_ft_common.c / .h
• Command-specific parsing in valkey_glide_ft_commands.c
• Method macros invoked in valkey_z_php_methods.c (standalone) and valkey_glide_cluster.c (cluster)
• Build registration in config.m4 and package.xml

Limitations

• Tests require a Valkey server with the Search module loaded. Without it, tests skip gracefully.
• The alias test (testFtAliasOperations) is currently skipped — valkey-search 1.2 images don't support FT.ALIASADD yet. Will re-enable once newer images are available.
• The aggregate test (testFtAggregateBicycles) is also skipped due to query syntax differences in valkey-search 1.2. Same plan.

Testing

Integration tests in tests/ValkeyGlideValkeySearchTest.php covering:

• Index creation with various field types (TEXT, NUMERIC, TAG, VECTOR) and options
• Duplicate index error handling
• Drop and list round-trip
• KNN vector search with PARAMS and RETURN
• Search on non-existent index (error path)
• ftInfo with scope and shard flags
• Index-level options: SCORE, LANGUAGE, SKIPINITIALSCAN, NOSTOPWORDS, MINSTEMSIZE, NOOFFSETS
• Field options: nostem, sortable, weight, withsuffixtrie, nosuffixtrie
• RETURN with field aliases
• Alias lifecycle (add, list, update, delete, error on duplicate/non-existent) — skipped pending image support
• GROUPBY + REDUCE aggregate pipeline — skipped pending image support

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one issue.
• Commit message has a detailed description of what changed and why.
• Tests are added or updated.
• CHANGELOG.md and documentation files are updated.
• Destination branch is correct - main or release
• Create merge commit if merging release branch into main, squash otherwise.