docs: Add HTTL command reference page (#513)

* Initial plan

* Add HTTL command documentation page

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* Remove Simple error reply section and Parameters table from HTTL docs

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* Update HTTL docs: remove HPTTL note, add FIELDTTL to related commands

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* Fix FIELDTTL link to point to generic/fieldttl.md

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* Fix Array reply link to use valkey.io/topics/protocol/#arrays

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---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: romange <3674760+romange@users.noreply.github.com>

Author: Copilot

docs/command-reference/hashes/httl.md

@@ -0,0 +1,85 @@
+---
+description: "Learn how to use the HTTL command to query the remaining TTL of individual fields within a Redis hash, enabling granular cache management."
+---
+
+import PageTitle from '@site/src/components/PageTitle';
+
+# HTTL
+
+<PageTitle title="Redis HTTL Command (Documentation) | Dragonfly" />
+
+## Syntax
+
+    HTTL key FIELDS numfields field [field ...]
+
+**Time complexity:** O(N) where N is the number of fields being queried
+
+**ACL categories:** @read, @hash, @fast
+
+Returns the remaining Time-To-Live (TTL) in seconds for one or more fields of a hash stored at `key`.
+This allows you to inspect when individual hash fields will expire without modifying them.
+
+Unlike `TTL`, which operates at the key level, `HTTL` operates at the field level.
+Field-level expiry is set via [`HEXPIRE`](./hexpire.md) or [`HSETEX`](./hsetex.md).
+
+## Return
+
+[Array reply](https://valkey.io/topics/protocol/#arrays): an array of integer replies, one per field, in the same order as the fields were requested:
+
+- Integer reply: `-2` if the field does not exist in the hash, or if the hash key itself does not exist.
+- Integer reply: `-1` if the field exists but has no associated expiration (it persists indefinitely).
+- Integer reply: a positive integer representing the remaining TTL in seconds.
+
+## Examples
+
+**Fields with no expiry, one non-existent field:**
+
+```shell
+dragonfly> HSET myhash field1 "hello" field2 "world"
+(integer) 2
+dragonfly> HTTL myhash FIELDS 3 field1 field2 nosuchfield
+1) (integer) -1
+2) (integer) -1
+3) (integer) -2
+```
+
+**Setting an expiry and checking the remaining TTL:**
+
+```shell
+dragonfly> HEXPIRE myhash 30 FIELDS 1 field1
+1) (integer) 1
+dragonfly> HTTL myhash FIELDS 2 field1 field2
+1) (integer) 29
+2) (integer) -1
+```
+
+**Key does not exist — all fields return `-2`:**
+
+```shell
+dragonfly> HTTL no-key FIELDS 2 field1 field2
+1) (integer) -2
+2) (integer) -2
+```
+
+**Wrong key type:**
+
+```shell
+dragonfly> SET mystring "value"
+"OK"
+dragonfly> HTTL mystring FIELDS 1 field1
+(error) WRONGTYPE Operation against a key holding the wrong kind of value
+```
+
+## Notes
+
+- `HTTL` is a read-only command and does not modify the hash or any field TTLs.
+- The reported TTL reflects the time remaining at the moment the command is executed. For precise expiry management, consider the clock resolution on the server.
+- To remove an expiry from a field (make it persist), re-set the field without an expiry using [`HSET`](./hset.md).
+
+## Related Commands
+
+- [`HEXPIRE`](./hexpire.md) — Set a TTL on one or more hash fields.
+- [`FIELDTTL`](../generic/fieldttl.md) — Retrieve the TTL of a specific field.
+- [`HSETEX`](./hsetex.md) — Set hash field values along with a TTL.
+- [`HSET`](./hset.md) — Set hash field values (no expiry).
+- [`HGETALL`](./hgetall.md) — Retrieve all fields and values of a hash.