add_packet_filters via async Gx CCR-U ADDITION + Update Bearer (#22 Increment 4)

[next-nf]

Stacked on #53 (base async-ue-bearer-22-inc3). Fourth increment of #22.

Handles a UE add_packet_filters Bearer Resource Command: report the new filters' content to the PCRF over a Gx CCR-Update (Packet-Filter-Operation = ADDITION), await the rule install, and emit a PTI-echoing Update Bearer Request with the expanded TFT — replacing the true -> reject add_packet_filters hit before. An add never empties a bearer, so its outcome is always Increment 3's Update path.

Mostly reuse

The new code is narrow; the multi-await Update machinery is all Inc3:

• 6474658 — smf_tft: filter_to_flow_info now carries Precedence; new flow_info_to_pf_add_group/1 remaps a flow-info map into a Gx Packet-Filter-Information ADD group — Packet-Filter-Content (the IPFilterRule, already produced by format_flow_description) + Precedence + Flow-Direction, dropping the UE's TFT id (not a PCRF SDF handle). Includes a real diameter encode/decode round-trip (diameter_Gx_SUITE) — the wire-shape validation the Inc2 mock path never exercised; it confirmed bare grouped-members encode cleanly (and gives the Inc2 delete group coverage by proxy).
• 5dfba6f — pgw_s5s8: extracts Inc3's Update path into a shared ue_update_outcome/7 (a byte-for-byte pure move; the Inc3 delete e2e is the guard), adds ue_add_filters_proc/4 (ADDITION content groups, install-only fold, unconditional Update) and the add_packet_filters dispatch arm. Reuses emit_ue_update_bearer/await_pfcp_modify/detect_modified_bearers/send_dedicated_bearers_update/br_ok/br_err/ccr_result/fold_cca verbatim.

Reviews & tests

• Task 1 review Approved (the reviewer independently verified the bare-vs-list encoding against OTP diameter source: optional-arity fields get forgiving auto-wrap, decode always list-wraps). Task 2 review Approved (extraction confirmed a pure move; e2e non-vacuous with a genuine RED + real TAD encode/decode round-trip; the install answer's {QCI,ARP} matched to the bearer so it grows rather than creates).
• pgw_SUITE 131/131 (130 prior + 1 new add case), independently re-run; the Inc2/Inc3 delete regression stays green (the extraction is behaviour-preserving). smf_tft_SUITE 26/26, diameter_Gx_SUITE 8/8. Default compile green.

Out of scope

replace_packet_filters (Increment 5 — needs the Gx MODIFICATION-vs-delete+add semantics grounded); requested-QoS/GBR (Increment 6). An add whose PCRF response binds a new {QCI,ARP} (→ a new bearer) is out of scope — the add proc handles add-to-existing (→ Update) and acks gracefully otherwise.

[next-nf]

Superseded by the async-invoke restack. This increment was re-authored onto invoke(pipeline_async) and collapsed into #56 (delete/add/replace together) on the redone #48 foundation. Closing in favor of #56.